July 18, 2025 • 40 mins
Lying on the cold metal table, Voyne Ray Cox knew the drill. This was his ninth round of cancer treatment - which is why he was certain that what happened next couldn't be right. He heard a sizzling sound and saw a blue flash. And then - agony. It was like someone had thrust a hot skewer through his shoulder. He cried out in pain, but the operator was down the corridor and she couldn't hear him. She blasted him again and again with the red-hot radiation beam.
Ray wasn't the first patient to be burned by the Therac-25 therapy machine, and he wouldn't be the last. Its dual-purpose design, controlled by a software programme, was supposed to offer hospitals more bang for their buck. But as patient after patient suffered ulcerated skin and yawning lesions, it should have been clear that something was horribly wrong. Why did it take so long for anyone to put this awful puzzle together?
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:15):
Pushkin. Nobody really wants to be deliberately bombarded with radiation,
but if you have cancer, radiation therapy might just save
your life. That must have been what a young man
called Voyin Ray Cox hoped as he made visit after
(00:37):
visit to the East Texas Cancer Center. Just thirty three
years old, Ray, to his friends, was young to be
a cancer survivor. He had a tumor cut out of
his shoulder, and now March nineteen eighty six, he was
there for his ninth session of radiation therapy designed to
(00:58):
ensure that no traces of the cancer remained. Despite his
bad luck, Ray was a cheerful, resilient man. He knew
the drill, press his bare chest and stomach onto the
cold metal treatment table, chat to the operator while she
maneuvered him into position underneath the looming bulk of the
(01:21):
THEAK twenty five radiation therapy machine. The operator knew the
drill too. In his account of the case, the ergonomics
expert Stephen Casey calls her Mary Beth, although that's not
her real name, will do the same. Mary Beth cheerfully
(01:44):
caught up with Ray as she used a console control
to precisely position him under the THAK twenty five's radiation beamgun.
Then she walked down the corridor to the control room,
which was at a safe distance. Ordinarily, the control room
and the treatment room would be linked up by CCTV
(02:04):
and microphones, but neither the cameras nor the audio were
connected that day, and that didn't seem to matter. Normally,
they'd be useful for some reassuring chat or to give
the patient a word of instruction, and Ray, being an
old hand, didn't need any of that. Mary Beth typed
(02:26):
the treatment instructions into the computer a series of letters.
She pressed X to choose the mode, then straightway realized
her mistake. Ray needed the other mode. She deleted the
X and pressed E should check the instructions. They were
all correct, beam ready, the computer told her. She pressed
(02:49):
B to administer the treatment. Down the hall. On the
treatment table, Ray Cox heard a sizzling sound and saw
a blue flash and then agony. It was like someone
had thrust a hot skewer through his sh shoulder. This
(03:10):
wasn't right. He knew it couldn't be right. The last
eight treatments had been nothing like this. Back in the
control room, Mary Beth couldn't hear Ray's cry of pain,
and she couldn't see his body contorting on the treatment table.
All she saw was a bland little notification malfunction fifty four.
(03:34):
It wasn't clear what that meant. The machine would often
pause and produce an unexplained error code, sometimes thirty forty
fifty times a day. As one operator later commented, I
can't remember all the reasons it would stop, but there
were a lot of them. The machine indicated that Ray
(03:57):
had received only a tiny fraction of the intended dose,
and Mary Beth had been assured that the Therak twenty
five had so many safeguards it was almost impossible to
overdose a patient. It only took a single keypress for
her to reset the machine and try again. I'm Tim Harford,
(04:19):
and you're listening to cautionary tales. Mary Beth was an
(04:46):
experienced operator of for Ferrak twenty five. She must have
seen it crash and pop up an error message ten
thousand times or more. Although she didn't know what those
error messages meant. How could she? The machine's manual didn't
explain them, it didn't even mention them. Because she'd been
(05:08):
in that position so many times. It took her mere
seconds to reset the machine for another try at giving
Ray his treatment. That wasn't enough time for Ray to
get off the table. He'd rolled onto his side, but
mary Beth, of course couldn't see that, and she couldn't
hear his agonized yelling. The machine fired again, another flash
(05:33):
of blue light, Another sizzled, and this time a hot
skewer went through Ray's neck. He was in too much
pain even to scream. Then the agony started to fade.
He gulped in some air and blew it out again.
Tried to calm himself, Hey, are you pushing the long bottom?
(05:58):
But mary Beth couldn't hear him. Something had gone wrong
with the Tharak twenty five. But what loyal listeners to
cautionary tales will be familiar with the Swiss cheese model
(06:20):
of accidents, made famous by the psychologist James Reason. Imagine
slices of Swiss cheese with those distinctive holes in them.
Each slice represents some kind of safeguard against an accident.
Maybe it's a fail safe in the hardware of a system,
so it simply won't work if the right pieces aren't
(06:40):
in position. Maybe it's a subroutine in the software, monitoring
what the system's doing and shutting it down if another
part of the software happens to glitch. But no safeguard
is perfect. Every slice of cheese has holes in it.
In James Reasons model, an accident becomes possible when all
(07:03):
the holes line up. That means that every safeguard in
the system becomes simultananeously vulnerable to the same kind of problem.
To prevent accidents, then get extra lines of defense and
try to strengthen the defenses you already have. To put
it another way, get more slices of cheese with fewer
(07:24):
holes in them. So did the THEAC twenty five need
better hardware or better software to prevent the accident that
happened to ray Cox? As it turns out, yes, but
that's also the wrong question. We should be looking at
a different kind of cheese slice. Altogether. Nine months before
(07:50):
ray Cox's excruciating experience, in July nineteen eighty five, forty
year old Francis Hill arrived at the Ontario Cancer Foundation
Clinic for her twenty fourth round of radiation treatment for
cervical cancer. The clinic was using a twenty five machine,
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but there was a problem the machine didn't seem to
be working. Every time the operator tried to fire the
radiation beam, the machine paused, produced an error message and
reported that no dose had been given. The operator hit
the pea key to proceed, and the same thing happened.
(08:31):
The operator hit p again, and it happened again. We've
all been there, clicking an icon on a screen, finding
that nothing seems to happen, and then clicking it again.
After four attempts, the operator called a technician who couldn't
find anything wrong with the Thearact twenty five. Francis Hill
(08:52):
left and the machine was used successfully on half a
dozen other patients that afternoon. That sort of thing wasn't
particularly strange, the operator reflected. The fair Act twenty five
would often seem to glitch like that, produce mysterious error messages,
and then suddenly working again for no particular reason. But
(09:17):
while glitches didn't seem strange to the operator, something seemed
strange to Francis. She could feel a kind of burning, tingling,
electric shock kind of sensation in her hip near where
the therapeutic beam had been aimed. When she came back
for another round of treatment three days later, her doctors
(09:40):
immediately diagnosed a radiation burn in her hip, which was
painfully swollen. They called the machines manufacturers to report a
suspected radiation overdose. The manufacturers were Atomic Energy of Canada
Limited AECL of radiation overdose. AECL had never heard of
(10:05):
anything like that before Strange. They sent a engineer along
to investigate. The FARACT twenty five could be used in
two different modes. The electron mode attacked cancer near the
surface of the patient's body. The machine emitted a beam
(10:26):
of electrons spread out by an array of magnets. The
X ray mode attacked cancer deep inside a patient's body.
The magnet array would be moved aside and replaced by
a device called a flattener, which focused the X ray
beam precisely on the cancer. The flattener absorbed a lot
(10:48):
of energy, which meant the X ray beam had to
be very powerful. The components which diffused the electron beams
or focused the X rays on the FAACT twenty five
were positioned on a turntable. As the machine was programmed
to fire either electrons or X rays at the patient's tumor,
(11:08):
the turntail would rotate automatically to fix the right component
into position. At least that was the idea. Two types
of radiation beam then one that needs diffusing, one that
needs focusing. If this sounds like an accident waiting to happen,
well it was. But machines like the THEAK twenty five
(11:32):
are expensive, and this dual purpose design meant that hospitals
got more bang for the buck. As long as the
right component was in place for the right beam, there
would be no problem. The THEAK twenty five was fully
controlled by a computer, unremarkable these days, but radical for
(11:53):
the mid nineteen eighties. Its predecessors, the THEAK six and
the THEAK twenty allowed a human operator to physically position
the magnets or the flattener. On the THEAK twenty five,
this manual position was replaced by servo motors, computer controlled
to quickly and precisely put everything in position. When AECL
(12:19):
investigated the incident with Francis Hill, they weren't actually able
to reproduce the error, but they suspected that the turntable
system hadn't worked properly. The turntable had three tiny switches
designed to measure when it was in position, but it
emerged that a single bit of error the computer glitching
(12:40):
and mistaking a zero for a one could produce a
faulty reading of the turntable's position. So AECL told the
clinics that used the THEAAK twenty five to visually confirm
before each procedure that the turntable was in the correct position,
just as a precaution until further notice. They tightened up
(13:03):
the software, making it more robust to a small error
like that. Then they got back in touch with the clinics.
No need for those visual checks anymore. We've just made
the machine five orders of magnitude safer, which in plain
English means it's about one hundred thousand times safer than before.
And it was safe already. But one thing AECL don't
(13:28):
seem to have done is to have notified the clinics
that an accident had happened and that a patient had
been injured by the machine. The clinics, at least say
they weren't told of any injuries. When AECL announced that
they'd fixed the problem, it was September nineteen eighty five.
A month later, they were sued by a woman named
(13:51):
Katie Yarborough. AECL had never heard of Katie Yarborough, who
was Katie Yarborough. Cautionary tales will return after the break.
(14:13):
Katie Yarborough's injury happened seven weeks before Francis Hills, early
in the summer of nineteen eighty five. She was being
treated at the Kenniston Oncology Center in Marietta, Georgia. Katie
was sixty one. She'd had a malignant tumor removed from
her breast, and now she needed follow up treatment to
(14:35):
destroy any secondary tumors which might have spread to the
lymph nodes under her collar bone. That treatment, of course,
would be provided by a Therak twenty five machine. But
when the technician fired up the Therak twenty five, Katie
felt an agonizing pain, a tremendous force of heat. This
(14:58):
red hot sensation. You burned me, Katie, exclaimed the technician,
who was puzzled. That shouldn't be possible. The technician said
the twenty five was safe, and there wasn't any sign
of a burn. Perhaps Katie's clavicle was a little warm
to the touch, but otherwise nothing seemed to be a miss.
(15:21):
The physicist at the Keniston Center was a man called
Tim Still. When he was informed, he was just as puzzled.
Tim knew about the two treatment modes, the powerful X
ray fire through the flattener and the gentler electron beam
fired through the magnet array. Katie Yarborough had been treated
(15:41):
in the electron mode, but Tim still wondered if something
had gone wrong with the array. He called the manufacturers
AECL with a question, was there any way the electron
beam could be fired directly at a patient without the
magnetarray in position? After three days, AECL replied no. They
(16:04):
explained that was simply impossible. But somewhere along the line
AECL didn't seem to get the message that a patient
had been injured. Maybe Tim still didn't tell them, or
maybe he did but the message didn't get through to
the key decision makers. It's quite possible that still didn't
(16:25):
even realize that Katie Yarborough was injured. After all. At
first she seemed fine, But Katie Yarborough wasn't recovering from
that mysterious burn. In fact, her symptoms were getting worse.
The skin above her left breast had reddened, her shoulder
would freeze up, and she suffered excruciating spasms. Her doctors
(16:50):
were baffled. They continued sending her for theac treatment. After all,
with malignant breast cancer, you can't afford to take risks.
But when her skin started to fall off, Katie refused
to continue lying on the treatment table underneath that machine.
And when Tim Still later examined Katie, he noticed something strange.
(17:16):
Not only did Katie seem to have a severe burn
to her upper chest, but her upper back we was
starting to Redden two. It was as though whatever had
burned her had passed right through her body and caused
an exit wound. When Francis Hill was injured, her clinicians
(17:42):
didn't know about the injury to Katie Yarborough, and as
hospitals across North America continued to use the THERAK twenty five,
they didn't know about Francis Hill or Katie Yarborough. They
only knew that the machine was already safe and had
just become one hundred thousand times safer. And that makes
(18:03):
what happened next almost inevitable. In December nineteen eighty five,
Dora Moss, a patient at the Yakima Valley Memorial Hospital
in Washington State, complained that her right hip seemed red
and inflamed in a distinctive striped pattern. Dora's doctors were puzzled.
(18:29):
It wasn't clear what could have caused the inflammation, although
possibly it was a perfectly normal reaction to the course
of radiation therapy she was having on her hip. Which
device was being used, funny you should ask. It was
a THERAC twenty five, But because the hospital staff at
(18:49):
Yakima weren't aware of the history of accidents, they were baffled.
Some of them wondered whether a slotted component on the
THERAK twenty five might explain the striped pattern. Others suspected
that it was a burn caused by Dora's habit of
sleeping with an electric heating pad. Maybe those heated wires
(19:11):
had slowly burned her skin, although on closer inspection the
arrangement of wires in the heating pad didn't actually match
the sore stripes on Dora's hip. So they contacted AECL
who responded.
Speaker 2 (19:28):
After careful consideration, we are of the opinion that this
damage could not have been produced by any malfunction of
the FARAC twenty five or by any operator error, So
that was it.
Speaker 1 (19:43):
Then, Officially, the cause of that stripeye burn was cause unknown,
But if the cause was unclear. The consequences were stark.
Dora Moss needed surgery and skin grafts to patch up
her ulcerated skin and treat her chronic pain. Maybe it
(20:04):
wasn't the FAAC twenty five. It certainly wasn't a burn
from a heating pad. The Yakima hospital staff were even
told that there'd been no other incidents with the THERAK
twenty five. Was anyone putting all these incidents together and
spotting a pattern, It seems not, although it's hard to
(20:28):
be sure. Nancy Levison, software safety expert and the author
of a definitive account of the affair, explains that because
there was never an official investigation, it's often unclear who
exactly knew what and when they knew it. At the
(20:49):
East Texas Cancer Center in March nineteen eighty six, three
months after the injury to Dora Moss, Mary Beth was puzzled.
She'd tried twice to administer the treatment to ray Cox,
apparently without success. Third time, lucky she hit again. Ray
(21:11):
Cox had been trying to ease himself off the table,
but when that searing skewer feeling hit him for a
third time, jabbing through his neck and shoulder. He leapt
for safety, barged open the door, and ran to the
nurses station. When Mary Beth emerged, Ray was obviously shaken
(21:32):
by what had happened. He told her that he felt
like had been given three separate powerful electric shocks. How strange,
Mary Beth reassured him that the machine had automatically shut
down and according to the computer's display panel, Ray had
only received one tenth of the intended dose. Mary Beth
(21:55):
informed Ray's doctor and the center's physicist, Fritz Hager about
the electric shocks. They came to examine the machine and Ray.
There seemed to be nothing wrong with either of them,
but that's the nature of a radiation overdose. It's invisible
and at first the injuries it causes who are invisible too.
(22:18):
Ray looked fine, but he really wasn't. Hagar called the
manufacturer of the machine AECL to apport the incident. Then
he ran through some tests and since everything seemed to
be in order, pronounced the machine good to go for
the afternoon patients who were waiting for treatment, and everything
(22:39):
went smoothly. That's what happened. Remember, the THERAK twenty five
often produced mysterious error messages. And then suddenly started to
work again for no obvious reason. Three weeks after the
strange incident with Ray Cox, Mary Beth had a new patient,
(23:03):
sixty six year old Vernon Kidd, who had a tumor
on his ear. As soon as the treatment beam was activated,
Vernon cried out and started moaning for help. This time,
the audio link was working. What happened, asked Mary Beth.
Speaker 2 (23:24):
Fire.
Speaker 1 (23:25):
He replied, fire on the side of his face. When
the physicist Fritz Hager arrived on the scene, Vernon elaborated
he'd heard a sound like frying eggs and a flash
of light and then pain. He was confused and upset.
What happened to me? We'll find out what happened to
(23:48):
Vernon Kidd after the break. September ninth, nineteen forty seven,
computer scientists at Harvard University get to the bottom of
(24:09):
why their fancy computer, the Mark two, is malfunctioning. It's
a bug, a literal bug, a moth in fact, which
has crawled into the mass of electrical relays in the
room sized computing machine and caused a short circuit. The
logbook tells the tale. Handwritten on blue gridded paper are
(24:30):
the words relay seventy panel f moth in relay. Next
to those words, the bug itself is preserved under a
short length of yellowing sticky tape underneath the dry remark.
First actual case of bug being found. Software bugs are
(24:53):
the bane of programmers, although as that punchline implies, this
wasn't the first time the word bug had been used
to describe a device malfunctioning. It was just the first
time that an insect had been obliging enough to turn
the metaphor into reality. In fact, software bugs are older
than computers. The first computer program is widely thought to
(25:15):
have been written by Ada Lovelace, an English mathematician and
friend of the engineer Charles Babbage. In eighteen forty three,
Lovelace published an algorithm that would enable Babbage's proto computer,
the Analytical Engine, to calculate a particular sequence of numbers.
What's so striking about Lovelace's algorithm is that the Analytical
(25:39):
Engine had not been built, nor would it ever be.
Babbage's designs were just too ambitious, and nobody would be
able to construct a general purpose computer for another century.
But modern analysis concludes that if Lovelace's program ever had
been run on an analytical engine. It wouldn't have worked,
(26:03):
not first time anyway, because there was a typo. Not
only had Lovelace published the first software she had also
published the first software bug. Anyone who's had the experience
of writing computer code, or even for gen x as
(26:26):
like me, of typing in a computer program printed in
the pages of a magazine will know what it's like
to have a bug. In some cases, the bugs are
easily fixed. You run the program and it doesn't work.
Maybe the computer even tells you where things went off
the rails, exactly where the error was, or maybe not,
(26:50):
because some bugs are more like an unsuspected hole in
one of James Reasons slices of cheese. They sit there,
hidden by other slices, causing no trouble until the holes
and the slices aligne and the computer crashes. You may
(27:10):
not know why it crashed. You may be able to
restart the program and find it runs with no trouble,
but somewhere under the surface, the bug is still there.
Two of Fritz Hager's patients had apparently been electrocuted, and
(27:32):
while the Farak twenty five seemed to be working perfectly well,
he wasn't going to risk a third. He shut the
machine down, notified AECL, and then tried to figure out
what had occurred. It wasn't easy. After each incident, the
machine seemed to be working just fine. Hager and mary
(27:56):
Beth worked together trying to figure out what had triggered
the malfunction fifty four message. Eventually they succeeded. Mary Beth
recalled how she had originally typed X to use the
THURAC twenty five in X ray mode, then realized she
(28:17):
should have typed E. Quickly using the cursor keys to
move to the correct box. She corrected the entry to E,
repeatedly hit return to accept all the other treatment variables
which were correct, and awaited the message beam ready. What
she hadn't known, what nobody had known, is that a
(28:40):
quick edit like that confused the computer's subroutines, which checked
the setup only at certain moments. The result, the beam
was set to full X ray power, but the flattener
that would absorb most of the radiation wasn't in position.
(29:00):
To make matters even worse, the Thorax software was confused
by this dangerous setup and didn't correctly monitor the dose administered.
It was a particular sequence of keystrokes that caused the
problem an unlikely sequence, but not an inconceivable one. It
(29:21):
shouldn't be particularly surprising that experienced operators such as Mary
Beth might type the wrong mode, notice the error, then
swiftly correct it. It was the swiftness of that correction
that bewildered the software. Fritz Hager explained to AECL that
(29:42):
he could now reproduce the error on demand. The AECL
engineer couldn't until Hager explained that all the keystrokes had
to be entered in less than eight seconds. The next day,
the AECL engineer called back, Yes, he could now replicate
(30:06):
the error, and he had bad news. If the beam
was fired in such conditions, the patient would receive a
dose of twenty five thousand rads, more than one hundred
times more than intended, which potentially could be fatal. Over
(30:32):
the course of three weeks, sixty six year old Vernon
Kid moved from disorientation to a coma to death. The
autopsy revealed that the section of his brain running from
under his right temple to behind his right ear had
been withered by a high dose of radiation. It's natural
(31:05):
to describe the problem with a Tharak twenty five as
a software bug, and while that's true, it doesn't really
help us understand the problem or prevent similar problems in future.
As Nancy Levison writes, virtually or complex software can be
made to behave in an unexpected fashion under some conditions.
(31:29):
Demanding software with no bugs is like demanding a slice
of Swiss cheese with no holes. It's in the nature
of Swiss cheese that there will always be holes, and
it's in the nature of complex software that there will
always be bugs. The question is what happens when a
(31:49):
bug appears. Perhaps another part of the software is able
to spot the problem. A separate slice of software cheese
that didn't happen With a Therac twenty five. The computer
would tell the operator what dose the patient had received.
There was no direct measurement of that dose. The bug
(32:10):
that led to the overdose also led to the software
failing to report the overdose, or perhaps there are failsafes
in the hardware. Again, not with the Therrak twenty five,
the machine relied on the software being perfect. The shielding
components were put in place by the software. The decision
(32:32):
to allow the electron gun to fire or not was
made by the software, and the dose the patient received
was reported by the software. If the software was wrong
about one of these things, it could easily be wrong
about the others. There is a different approach. The THEAK twenty,
(32:55):
the predecessor of the THERAK twenty five, was designed to
operate with or without a computer, and it was built
with mechanical interlocks. If you tried to fire the beam
without the right component in place, the machine just wouldn't
do it. It was only after the THEAK twenty five's
(33:15):
problems became widely known that something began to dawn on
THEA'AC twenty users. Sometimes the machine's fuse would blow after
quick edits I was annoying and a bit mysterious. The
machine would have to be switched off, the fuse replaced,
and everything restarted. The fra AC twenty software had been
(33:39):
built on the same codebase as the fair AC twenty five,
and on closer examination it became clear that the THEA
ACT twenty had the same software bug. Because of the
mechanical interlocks, which would physically prevent the machine from working
unless it was correctly set up, the bug was never
(34:00):
anything more than an annoyance. The most precious thing that
was damaged was a fuse. The Fair Act twenty five
five needed better software, and it needed better hardware. But
as I said earlier, that's also the wrong place to focus.
Another kind of cheese slice was missing. There was no
(34:24):
proper process for noting anomalous incidents, suspected malfunctions, or possible injuries.
Hospitals should have been reporting both the strange incidents and
the later mysterious injuries. Someone either AECL or a regulator
should have been collecting and analyzing the reports. Because that
(34:47):
didn't happen, every new incident caused a new wave of
muddle and bewilderment. Of course, we should try hard to
eliminate bugs, especially when lives are at stake. But the
real lesson here is that safety is not a function
(35:08):
of good software alone. It's the function of the whole system,
and the system goes beyond the software. In fact, it
goes beyond the machine. The system includes the network of
people who make the machine, use the machine, and regulate
the machine. In this case, they should have been keeping
(35:28):
each other closely informed. They weren't, and as a result,
it took months for anyone to assemble the pieces of
this awful puzzle Voin. Ray Cox was young and strong,
but he had taken a triple blast of high dose
(35:51):
radiation to his back, shoulder, and neck. Before long, he
was starting to spit up blood. The awful radiation burns
on his back and neck turned into yawning lesions as
the skin and flesh started to peel off his body.
While over the weeks that followed, the damage to his
(36:13):
spinal column paralyzed his left arm, both legs, and his
vocal cords, ray tried to keep his sense of humor.
Before he lost his ability to speak, he would joke
to friends and family Captain Kirk forgot to put the
machine on stun. Ray Cox died in August nineteen eighty six,
(36:41):
a few months after the accident, and five months after that,
Glenn Dodd, a sixty five year old cancer sufferer, was
given radiation therapy at Yakima Valley Memorial Hospital, where Dora
Moss had acquired those mysterious striped radiation burns after treatment
(37:03):
from a THERAK twenty five. Glen Dodd was being treated
by a THEAK twenty five, he received a fatal overdose.
Dodd was terminally ill, but doctors concluded that the injuries
he had suffered from the malfunctioning machine had killed him
(37:25):
before his own cancer could. Why hadn't aecl fixed the
software fault? Well? As it happens, Glen do Odd wasn't
killed by the glitch that had killed ray Cox and
Vernon Kidd, but by a different software error. You see,
(37:49):
there's always another bug lying in wait for the moment
to strike. This isn't the first cautionary tale we've done
about radiation overdoses. Two of my very favorite episodes of
(38:10):
the podcast were Glowing Peril, The magical glitter that poisoned
a City, and How the Radium Girls Fought Back, two
unforgettable episodes which came out as a pair late in
twenty twenty three. You may enjoy listening to them. I
first heard about ray Cox's case from Stephen M. Casey's
(38:33):
book Set Phases on stun while the definitive authority on
the THERAK twenty five case is Nancy Levison's investigation, written
with Clark Turner. For a full list of our sources,
see the show notes at Timharford dot com. Cautionary Tales
(38:58):
is written by me Tim Harford with Andrew Wright. The
show is produced by Alice Fines with Marilyn Rust. The
sound design and original music are the work of Pascal Wye.
Sarah Nix edited the script. Cautionary Tales features the voice
talents of Ben Crow, Melanie Gushridge, Stella Harford, Gemma Saunders
(39:19):
and Rufus Wright. The show wouldn't have been possible without
the work of Jacob Weisberg, Ryan Dilly, Greta Cohne, Eric Sandler,
Carrie Brody, Christina Sullivan, Kira Posey and Owen Miller. Cautionary
Tales as a production of Pushkin Industries. It's recorded at
Wardoor Studios in London by Tom Berry. If you like
(39:43):
the show, please remember to share, rate and review. It
doesn't really make a difference to us and if you
want to hear the show ad free, sign up to
Pushkin Plus on the show page on Apple Podcasts or
at pushkin dot Fm, slash plus, st
Pushkin. Nobody really wants to be deliberately bombarded with radiation,
but if you have cancer, radiation therapy might just save
your life. That must have been what a young man
called Voyin Ray Cox hoped as he made visit after
(00:37):
visit to the East Texas Cancer Center. Just thirty three
years old, Ray, to his friends, was young to be
a cancer survivor. He had a tumor cut out of
his shoulder, and now March nineteen eighty six, he was
there for his ninth session of radiation therapy designed to
(00:58):
ensure that no traces of the cancer remained. Despite his
bad luck, Ray was a cheerful, resilient man. He knew
the drill, press his bare chest and stomach onto the
cold metal treatment table, chat to the operator while she
maneuvered him into position underneath the looming bulk of the
(01:21):
THEAK twenty five radiation therapy machine. The operator knew the
drill too. In his account of the case, the ergonomics
expert Stephen Casey calls her Mary Beth, although that's not
her real name, will do the same. Mary Beth cheerfully
(01:44):
caught up with Ray as she used a console control
to precisely position him under the THAK twenty five's radiation beamgun.
Then she walked down the corridor to the control room,
which was at a safe distance. Ordinarily, the control room
and the treatment room would be linked up by CCTV
(02:04):
and microphones, but neither the cameras nor the audio were
connected that day, and that didn't seem to matter. Normally,
they'd be useful for some reassuring chat or to give
the patient a word of instruction, and Ray, being an
old hand, didn't need any of that. Mary Beth typed
(02:26):
the treatment instructions into the computer a series of letters.
She pressed X to choose the mode, then straightway realized
her mistake. Ray needed the other mode. She deleted the
X and pressed E should check the instructions. They were
all correct, beam ready, the computer told her. She pressed
(02:49):
B to administer the treatment. Down the hall. On the
treatment table, Ray Cox heard a sizzling sound and saw
a blue flash and then agony. It was like someone
had thrust a hot skewer through his sh shoulder. This
(03:10):
wasn't right. He knew it couldn't be right. The last
eight treatments had been nothing like this. Back in the
control room, Mary Beth couldn't hear Ray's cry of pain,
and she couldn't see his body contorting on the treatment table.
All she saw was a bland little notification malfunction fifty four.
(03:34):
It wasn't clear what that meant. The machine would often
pause and produce an unexplained error code, sometimes thirty forty
fifty times a day. As one operator later commented, I
can't remember all the reasons it would stop, but there
were a lot of them. The machine indicated that Ray
(03:57):
had received only a tiny fraction of the intended dose,
and Mary Beth had been assured that the Therak twenty
five had so many safeguards it was almost impossible to
overdose a patient. It only took a single keypress for
her to reset the machine and try again. I'm Tim Harford,
(04:19):
and you're listening to cautionary tales. Mary Beth was an
(04:46):
experienced operator of for Ferrak twenty five. She must have
seen it crash and pop up an error message ten
thousand times or more. Although she didn't know what those
error messages meant. How could she? The machine's manual didn't
explain them, it didn't even mention them. Because she'd been
(05:08):
in that position so many times. It took her mere
seconds to reset the machine for another try at giving
Ray his treatment. That wasn't enough time for Ray to
get off the table. He'd rolled onto his side, but
mary Beth, of course couldn't see that, and she couldn't
hear his agonized yelling. The machine fired again, another flash
(05:33):
of blue light, Another sizzled, and this time a hot
skewer went through Ray's neck. He was in too much
pain even to scream. Then the agony started to fade.
He gulped in some air and blew it out again.
Tried to calm himself, Hey, are you pushing the long bottom?
(05:58):
But mary Beth couldn't hear him. Something had gone wrong
with the Tharak twenty five. But what loyal listeners to
cautionary tales will be familiar with the Swiss cheese model
(06:20):
of accidents, made famous by the psychologist James Reason. Imagine
slices of Swiss cheese with those distinctive holes in them.
Each slice represents some kind of safeguard against an accident.
Maybe it's a fail safe in the hardware of a system,
so it simply won't work if the right pieces aren't
(06:40):
in position. Maybe it's a subroutine in the software, monitoring
what the system's doing and shutting it down if another
part of the software happens to glitch. But no safeguard
is perfect. Every slice of cheese has holes in it.
In James Reasons model, an accident becomes possible when all
(07:03):
the holes line up. That means that every safeguard in
the system becomes simultananeously vulnerable to the same kind of problem.
To prevent accidents, then get extra lines of defense and
try to strengthen the defenses you already have. To put
it another way, get more slices of cheese with fewer
(07:24):
holes in them. So did the THEAC twenty five need
better hardware or better software to prevent the accident that
happened to ray Cox? As it turns out, yes, but
that's also the wrong question. We should be looking at
a different kind of cheese slice. Altogether. Nine months before
(07:50):
ray Cox's excruciating experience, in July nineteen eighty five, forty
year old Francis Hill arrived at the Ontario Cancer Foundation
Clinic for her twenty fourth round of radiation treatment for
cervical cancer. The clinic was using a twenty five machine,
(08:11):
but there was a problem the machine didn't seem to
be working. Every time the operator tried to fire the
radiation beam, the machine paused, produced an error message and
reported that no dose had been given. The operator hit
the pea key to proceed, and the same thing happened.
(08:31):
The operator hit p again, and it happened again. We've
all been there, clicking an icon on a screen, finding
that nothing seems to happen, and then clicking it again.
After four attempts, the operator called a technician who couldn't
find anything wrong with the Thearact twenty five. Francis Hill
(08:52):
left and the machine was used successfully on half a
dozen other patients that afternoon. That sort of thing wasn't
particularly strange, the operator reflected. The fair Act twenty five
would often seem to glitch like that, produce mysterious error messages,
and then suddenly working again for no particular reason. But
(09:17):
while glitches didn't seem strange to the operator, something seemed
strange to Francis. She could feel a kind of burning, tingling,
electric shock kind of sensation in her hip near where
the therapeutic beam had been aimed. When she came back
for another round of treatment three days later, her doctors
(09:40):
immediately diagnosed a radiation burn in her hip, which was
painfully swollen. They called the machines manufacturers to report a
suspected radiation overdose. The manufacturers were Atomic Energy of Canada
Limited AECL of radiation overdose. AECL had never heard of
(10:05):
anything like that before Strange. They sent a engineer along
to investigate. The FARACT twenty five could be used in
two different modes. The electron mode attacked cancer near the
surface of the patient's body. The machine emitted a beam
(10:26):
of electrons spread out by an array of magnets. The
X ray mode attacked cancer deep inside a patient's body.
The magnet array would be moved aside and replaced by
a device called a flattener, which focused the X ray
beam precisely on the cancer. The flattener absorbed a lot
(10:48):
of energy, which meant the X ray beam had to
be very powerful. The components which diffused the electron beams
or focused the X rays on the FAACT twenty five
were positioned on a turntable. As the machine was programmed
to fire either electrons or X rays at the patient's tumor,
(11:08):
the turntail would rotate automatically to fix the right component
into position. At least that was the idea. Two types
of radiation beam then one that needs diffusing, one that
needs focusing. If this sounds like an accident waiting to happen,
well it was. But machines like the THEAK twenty five
(11:32):
are expensive, and this dual purpose design meant that hospitals
got more bang for the buck. As long as the
right component was in place for the right beam, there
would be no problem. The THEAK twenty five was fully
controlled by a computer, unremarkable these days, but radical for
(11:53):
the mid nineteen eighties. Its predecessors, the THEAK six and
the THEAK twenty allowed a human operator to physically position
the magnets or the flattener. On the THEAK twenty five,
this manual position was replaced by servo motors, computer controlled
to quickly and precisely put everything in position. When AECL
(12:19):
investigated the incident with Francis Hill, they weren't actually able
to reproduce the error, but they suspected that the turntable
system hadn't worked properly. The turntable had three tiny switches
designed to measure when it was in position, but it
emerged that a single bit of error the computer glitching
(12:40):
and mistaking a zero for a one could produce a
faulty reading of the turntable's position. So AECL told the
clinics that used the THEAAK twenty five to visually confirm
before each procedure that the turntable was in the correct position,
just as a precaution until further notice. They tightened up
(13:03):
the software, making it more robust to a small error
like that. Then they got back in touch with the clinics.
No need for those visual checks anymore. We've just made
the machine five orders of magnitude safer, which in plain
English means it's about one hundred thousand times safer than before.
And it was safe already. But one thing AECL don't
(13:28):
seem to have done is to have notified the clinics
that an accident had happened and that a patient had
been injured by the machine. The clinics, at least say
they weren't told of any injuries. When AECL announced that
they'd fixed the problem, it was September nineteen eighty five.
A month later, they were sued by a woman named
(13:51):
Katie Yarborough. AECL had never heard of Katie Yarborough, who
was Katie Yarborough. Cautionary tales will return after the break.
(14:13):
Katie Yarborough's injury happened seven weeks before Francis Hills, early
in the summer of nineteen eighty five. She was being
treated at the Kenniston Oncology Center in Marietta, Georgia. Katie
was sixty one. She'd had a malignant tumor removed from
her breast, and now she needed follow up treatment to
(14:35):
destroy any secondary tumors which might have spread to the
lymph nodes under her collar bone. That treatment, of course,
would be provided by a Therak twenty five machine. But
when the technician fired up the Therak twenty five, Katie
felt an agonizing pain, a tremendous force of heat. This
(14:58):
red hot sensation. You burned me, Katie, exclaimed the technician,
who was puzzled. That shouldn't be possible. The technician said
the twenty five was safe, and there wasn't any sign
of a burn. Perhaps Katie's clavicle was a little warm
to the touch, but otherwise nothing seemed to be a miss.
(15:21):
The physicist at the Keniston Center was a man called
Tim Still. When he was informed, he was just as puzzled.
Tim knew about the two treatment modes, the powerful X
ray fire through the flattener and the gentler electron beam
fired through the magnet array. Katie Yarborough had been treated
(15:41):
in the electron mode, but Tim still wondered if something
had gone wrong with the array. He called the manufacturers
AECL with a question, was there any way the electron
beam could be fired directly at a patient without the
magnetarray in position? After three days, AECL replied no. They
(16:04):
explained that was simply impossible. But somewhere along the line
AECL didn't seem to get the message that a patient
had been injured. Maybe Tim still didn't tell them, or
maybe he did but the message didn't get through to
the key decision makers. It's quite possible that still didn't
(16:25):
even realize that Katie Yarborough was injured. After all. At
first she seemed fine, But Katie Yarborough wasn't recovering from
that mysterious burn. In fact, her symptoms were getting worse.
The skin above her left breast had reddened, her shoulder
would freeze up, and she suffered excruciating spasms. Her doctors
(16:50):
were baffled. They continued sending her for theac treatment. After all,
with malignant breast cancer, you can't afford to take risks.
But when her skin started to fall off, Katie refused
to continue lying on the treatment table underneath that machine.
And when Tim Still later examined Katie, he noticed something strange.
(17:16):
Not only did Katie seem to have a severe burn
to her upper chest, but her upper back we was
starting to Redden two. It was as though whatever had
burned her had passed right through her body and caused
an exit wound. When Francis Hill was injured, her clinicians
(17:42):
didn't know about the injury to Katie Yarborough, and as
hospitals across North America continued to use the THERAK twenty five,
they didn't know about Francis Hill or Katie Yarborough. They
only knew that the machine was already safe and had
just become one hundred thousand times safer. And that makes
(18:03):
what happened next almost inevitable. In December nineteen eighty five,
Dora Moss, a patient at the Yakima Valley Memorial Hospital
in Washington State, complained that her right hip seemed red
and inflamed in a distinctive striped pattern. Dora's doctors were puzzled.
(18:29):
It wasn't clear what could have caused the inflammation, although
possibly it was a perfectly normal reaction to the course
of radiation therapy she was having on her hip. Which
device was being used, funny you should ask. It was
a THERAC twenty five, But because the hospital staff at
(18:49):
Yakima weren't aware of the history of accidents, they were baffled.
Some of them wondered whether a slotted component on the
THERAK twenty five might explain the striped pattern. Others suspected
that it was a burn caused by Dora's habit of
sleeping with an electric heating pad. Maybe those heated wires
(19:11):
had slowly burned her skin, although on closer inspection the
arrangement of wires in the heating pad didn't actually match
the sore stripes on Dora's hip. So they contacted AECL
who responded.
Speaker 2 (19:28):
After careful consideration, we are of the opinion that this
damage could not have been produced by any malfunction of
the FARAC twenty five or by any operator error, So
that was it.
Speaker 1 (19:43):
Then, Officially, the cause of that stripeye burn was cause unknown,
But if the cause was unclear. The consequences were stark.
Dora Moss needed surgery and skin grafts to patch up
her ulcerated skin and treat her chronic pain. Maybe it
(20:04):
wasn't the FAAC twenty five. It certainly wasn't a burn
from a heating pad. The Yakima hospital staff were even
told that there'd been no other incidents with the THERAK
twenty five. Was anyone putting all these incidents together and
spotting a pattern, It seems not, although it's hard to
(20:28):
be sure. Nancy Levison, software safety expert and the author
of a definitive account of the affair, explains that because
there was never an official investigation, it's often unclear who
exactly knew what and when they knew it. At the
(20:49):
East Texas Cancer Center in March nineteen eighty six, three
months after the injury to Dora Moss, Mary Beth was puzzled.
She'd tried twice to administer the treatment to ray Cox,
apparently without success. Third time, lucky she hit again. Ray
(21:11):
Cox had been trying to ease himself off the table,
but when that searing skewer feeling hit him for a
third time, jabbing through his neck and shoulder. He leapt
for safety, barged open the door, and ran to the
nurses station. When Mary Beth emerged, Ray was obviously shaken
(21:32):
by what had happened. He told her that he felt
like had been given three separate powerful electric shocks. How strange,
Mary Beth reassured him that the machine had automatically shut
down and according to the computer's display panel, Ray had
only received one tenth of the intended dose. Mary Beth
(21:55):
informed Ray's doctor and the center's physicist, Fritz Hager about
the electric shocks. They came to examine the machine and Ray.
There seemed to be nothing wrong with either of them,
but that's the nature of a radiation overdose. It's invisible
and at first the injuries it causes who are invisible too.
(22:18):
Ray looked fine, but he really wasn't. Hagar called the
manufacturer of the machine AECL to apport the incident. Then
he ran through some tests and since everything seemed to
be in order, pronounced the machine good to go for
the afternoon patients who were waiting for treatment, and everything
(22:39):
went smoothly. That's what happened. Remember, the THERAK twenty five
often produced mysterious error messages. And then suddenly started to
work again for no obvious reason. Three weeks after the
strange incident with Ray Cox, Mary Beth had a new patient,
(23:03):
sixty six year old Vernon Kidd, who had a tumor
on his ear. As soon as the treatment beam was activated,
Vernon cried out and started moaning for help. This time,
the audio link was working. What happened, asked Mary Beth.
Speaker 2 (23:24):
Fire.
Speaker 1 (23:25):
He replied, fire on the side of his face. When
the physicist Fritz Hager arrived on the scene, Vernon elaborated
he'd heard a sound like frying eggs and a flash
of light and then pain. He was confused and upset.
What happened to me? We'll find out what happened to
(23:48):
Vernon Kidd after the break. September ninth, nineteen forty seven,
computer scientists at Harvard University get to the bottom of
(24:09):
why their fancy computer, the Mark two, is malfunctioning. It's
a bug, a literal bug, a moth in fact, which
has crawled into the mass of electrical relays in the
room sized computing machine and caused a short circuit. The
logbook tells the tale. Handwritten on blue gridded paper are
(24:30):
the words relay seventy panel f moth in relay. Next
to those words, the bug itself is preserved under a
short length of yellowing sticky tape underneath the dry remark.
First actual case of bug being found. Software bugs are
(24:53):
the bane of programmers, although as that punchline implies, this
wasn't the first time the word bug had been used
to describe a device malfunctioning. It was just the first
time that an insect had been obliging enough to turn
the metaphor into reality. In fact, software bugs are older
than computers. The first computer program is widely thought to
(25:15):
have been written by Ada Lovelace, an English mathematician and
friend of the engineer Charles Babbage. In eighteen forty three,
Lovelace published an algorithm that would enable Babbage's proto computer,
the Analytical Engine, to calculate a particular sequence of numbers.
What's so striking about Lovelace's algorithm is that the Analytical
(25:39):
Engine had not been built, nor would it ever be.
Babbage's designs were just too ambitious, and nobody would be
able to construct a general purpose computer for another century.
But modern analysis concludes that if Lovelace's program ever had
been run on an analytical engine. It wouldn't have worked,
(26:03):
not first time anyway, because there was a typo. Not
only had Lovelace published the first software she had also
published the first software bug. Anyone who's had the experience
of writing computer code, or even for gen x as
(26:26):
like me, of typing in a computer program printed in
the pages of a magazine will know what it's like
to have a bug. In some cases, the bugs are
easily fixed. You run the program and it doesn't work.
Maybe the computer even tells you where things went off
the rails, exactly where the error was, or maybe not,
(26:50):
because some bugs are more like an unsuspected hole in
one of James Reasons slices of cheese. They sit there,
hidden by other slices, causing no trouble until the holes
and the slices aligne and the computer crashes. You may
(27:10):
not know why it crashed. You may be able to
restart the program and find it runs with no trouble,
but somewhere under the surface, the bug is still there.
Two of Fritz Hager's patients had apparently been electrocuted, and
(27:32):
while the Farak twenty five seemed to be working perfectly well,
he wasn't going to risk a third. He shut the
machine down, notified AECL, and then tried to figure out
what had occurred. It wasn't easy. After each incident, the
machine seemed to be working just fine. Hager and mary
(27:56):
Beth worked together trying to figure out what had triggered
the malfunction fifty four message. Eventually they succeeded. Mary Beth
recalled how she had originally typed X to use the
THURAC twenty five in X ray mode, then realized she
(28:17):
should have typed E. Quickly using the cursor keys to
move to the correct box. She corrected the entry to E,
repeatedly hit return to accept all the other treatment variables
which were correct, and awaited the message beam ready. What
she hadn't known, what nobody had known, is that a
(28:40):
quick edit like that confused the computer's subroutines, which checked
the setup only at certain moments. The result, the beam
was set to full X ray power, but the flattener
that would absorb most of the radiation wasn't in position.
(29:00):
To make matters even worse, the Thorax software was confused
by this dangerous setup and didn't correctly monitor the dose administered.
It was a particular sequence of keystrokes that caused the
problem an unlikely sequence, but not an inconceivable one. It
(29:21):
shouldn't be particularly surprising that experienced operators such as Mary
Beth might type the wrong mode, notice the error, then
swiftly correct it. It was the swiftness of that correction
that bewildered the software. Fritz Hager explained to AECL that
(29:42):
he could now reproduce the error on demand. The AECL
engineer couldn't until Hager explained that all the keystrokes had
to be entered in less than eight seconds. The next day,
the AECL engineer called back, Yes, he could now replicate
(30:06):
the error, and he had bad news. If the beam
was fired in such conditions, the patient would receive a
dose of twenty five thousand rads, more than one hundred
times more than intended, which potentially could be fatal. Over
(30:32):
the course of three weeks, sixty six year old Vernon
Kid moved from disorientation to a coma to death. The
autopsy revealed that the section of his brain running from
under his right temple to behind his right ear had
been withered by a high dose of radiation. It's natural
(31:05):
to describe the problem with a Tharak twenty five as
a software bug, and while that's true, it doesn't really
help us understand the problem or prevent similar problems in future.
As Nancy Levison writes, virtually or complex software can be
made to behave in an unexpected fashion under some conditions.
(31:29):
Demanding software with no bugs is like demanding a slice
of Swiss cheese with no holes. It's in the nature
of Swiss cheese that there will always be holes, and
it's in the nature of complex software that there will
always be bugs. The question is what happens when a
(31:49):
bug appears. Perhaps another part of the software is able
to spot the problem. A separate slice of software cheese
that didn't happen With a Therac twenty five. The computer
would tell the operator what dose the patient had received.
There was no direct measurement of that dose. The bug
(32:10):
that led to the overdose also led to the software
failing to report the overdose, or perhaps there are failsafes
in the hardware. Again, not with the Therrak twenty five,
the machine relied on the software being perfect. The shielding
components were put in place by the software. The decision
(32:32):
to allow the electron gun to fire or not was
made by the software, and the dose the patient received
was reported by the software. If the software was wrong
about one of these things, it could easily be wrong
about the others. There is a different approach. The THEAK twenty,
(32:55):
the predecessor of the THERAK twenty five, was designed to
operate with or without a computer, and it was built
with mechanical interlocks. If you tried to fire the beam
without the right component in place, the machine just wouldn't
do it. It was only after the THEAK twenty five's
(33:15):
problems became widely known that something began to dawn on
THEA'AC twenty users. Sometimes the machine's fuse would blow after
quick edits I was annoying and a bit mysterious. The
machine would have to be switched off, the fuse replaced,
and everything restarted. The fra AC twenty software had been
(33:39):
built on the same codebase as the fair AC twenty five,
and on closer examination it became clear that the THEA
ACT twenty had the same software bug. Because of the
mechanical interlocks, which would physically prevent the machine from working
unless it was correctly set up, the bug was never
(34:00):
anything more than an annoyance. The most precious thing that
was damaged was a fuse. The Fair Act twenty five
five needed better software, and it needed better hardware. But
as I said earlier, that's also the wrong place to focus.
Another kind of cheese slice was missing. There was no
(34:24):
proper process for noting anomalous incidents, suspected malfunctions, or possible injuries.
Hospitals should have been reporting both the strange incidents and
the later mysterious injuries. Someone either AECL or a regulator
should have been collecting and analyzing the reports. Because that
(34:47):
didn't happen, every new incident caused a new wave of
muddle and bewilderment. Of course, we should try hard to
eliminate bugs, especially when lives are at stake. But the
real lesson here is that safety is not a function
(35:08):
of good software alone. It's the function of the whole system,
and the system goes beyond the software. In fact, it
goes beyond the machine. The system includes the network of
people who make the machine, use the machine, and regulate
the machine. In this case, they should have been keeping
(35:28):
each other closely informed. They weren't, and as a result,
it took months for anyone to assemble the pieces of
this awful puzzle Voin. Ray Cox was young and strong,
but he had taken a triple blast of high dose
(35:51):
radiation to his back, shoulder, and neck. Before long, he
was starting to spit up blood. The awful radiation burns
on his back and neck turned into yawning lesions as
the skin and flesh started to peel off his body.
While over the weeks that followed, the damage to his
(36:13):
spinal column paralyzed his left arm, both legs, and his
vocal cords, ray tried to keep his sense of humor.
Before he lost his ability to speak, he would joke
to friends and family Captain Kirk forgot to put the
machine on stun. Ray Cox died in August nineteen eighty six,
(36:41):
a few months after the accident, and five months after that,
Glenn Dodd, a sixty five year old cancer sufferer, was
given radiation therapy at Yakima Valley Memorial Hospital, where Dora
Moss had acquired those mysterious striped radiation burns after treatment
(37:03):
from a THERAK twenty five. Glen Dodd was being treated
by a THEAK twenty five, he received a fatal overdose.
Dodd was terminally ill, but doctors concluded that the injuries
he had suffered from the malfunctioning machine had killed him
(37:25):
before his own cancer could. Why hadn't aecl fixed the
software fault? Well? As it happens, Glen do Odd wasn't
killed by the glitch that had killed ray Cox and
Vernon Kidd, but by a different software error. You see,
(37:49):
there's always another bug lying in wait for the moment
to strike. This isn't the first cautionary tale we've done
about radiation overdoses. Two of my very favorite episodes of
(38:10):
the podcast were Glowing Peril, The magical glitter that poisoned
a City, and How the Radium Girls Fought Back, two
unforgettable episodes which came out as a pair late in
twenty twenty three. You may enjoy listening to them. I
first heard about ray Cox's case from Stephen M. Casey's
(38:33):
book Set Phases on stun while the definitive authority on
the THERAK twenty five case is Nancy Levison's investigation, written
with Clark Turner. For a full list of our sources,
see the show notes at Timharford dot com. Cautionary Tales
(38:58):
is written by me Tim Harford with Andrew Wright. The
show is produced by Alice Fines with Marilyn Rust. The
sound design and original music are the work of Pascal Wye.
Sarah Nix edited the script. Cautionary Tales features the voice
talents of Ben Crow, Melanie Gushridge, Stella Harford, Gemma Saunders
(39:19):
and Rufus Wright. The show wouldn't have been possible without
the work of Jacob Weisberg, Ryan Dilly, Greta Cohne, Eric Sandler,
Carrie Brody, Christina Sullivan, Kira Posey and Owen Miller. Cautionary
Tales as a production of Pushkin Industries. It's recorded at
Wardoor Studios in London by Tom Berry. If you like
(39:43):
the show, please remember to share, rate and review. It
doesn't really make a difference to us and if you
want to hear the show ad free, sign up to
Pushkin Plus on the show page on Apple Podcasts or
at pushkin dot Fm, slash plus, st
Host
Tim Harford
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