How Agatha Christie Used Chemistry To Kill (In Books)

A new book explores the poisonous concoctions in Agatha Christie’s murder mysteries and the science behind how they kill.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:37Ira Flatow?

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• 1:08Flora Lichtman?

  Hey, it's Flora Lixman, and you are listening to Science Friday.

• 1:15Flora Lichtman?

  Today in the podcast, Death by Poison, with the mistress of mystery, the Duchess of Death, the Queen of Crime, Agatha Christie, who happened to be a chemistry nerd. You really have to be quite picky to find fault in her use of poisons. She is absolutely top quality in her scientific accuracy.

• 1:41Flora Lichtman?

  In about half of Agatha Christie's stories, poison is the murder weapon of choice. Dr. Katherine Harke, chemist turned author, explored those poisons in a new book, V's for Venom: Agatha Christie's Chemicals of Death. Katherine, welcome back to Science Friday. Thank you for having me. Katherine, this is not your first book about poisons, or even about Agatha Christie's poisons. What has brought you back to this well?

• 2:08Speaker 04

  Agatha Christie is so varied in her choice of poisons. Everyone seems to think it's just arsenic in the ubiquitous cups of tea, served at the vicar's table. It's not that. She is so imaginative and creative, not just in the choice of poisons, but how they're deployed, how they're detected, how signs are signalled to her readers and other characters within the book. So I had more than enough material to fill one book.

• 2:39Flora Lichtman?

  And you must love writing about the science of killing people.

• 2:42Speaker 04

  Oh, who wouldn't?

• 2:46Flora Lichtman?

  Well, how accurate is the poison science in Agatha Christie's books?

• 2:50Speaker 04

  I have to say she is top notch. You really have to be quite picky to find fault in her use of poisons. There are certain examples where she speeds up the effects or she exaggerates the detectability, perhaps, but it's, you know, you can understand that for the purposes of a story, nobody wants to read about eight hours of agonising stomach cramps. We want to get on with the plot. So I can understand some of the shortcuts, but generally speaking, she is absolutely top quality in her scientific accuracy.

• 3:27Flora Lichtman?

  Where did she learn about poisons?

• 3:29Speaker 04

  She trained during the First World War to be a dispenser in a hospital dispensary. So she was making up drugs and prescriptions by hand because there was nothing prepackaged, preweighed in, you know, the 1910s when the war was going on. So she just was surrounded by bottles of poisons that you had to accurately weigh out, mix together, effectively press into pills that would hold their shape long enough in the bottle, but disintegrate in the body to release their active component. So there is a technical skill in knowing what drugs can and can't be combined, but

• 4:09Speaker 04

  there is also an art in being able to blend and mix these compounds into usable products. So, and because- The risk of giving someone too much or the wrong drug is very high. It has very serious consequences. Obviously, you have to study very hard. You have to know what you're doing. So she had a very thorough background, not just in chemistry, but in pharmacy, as well as shadowing another pharmacist to understand the practicalities of this particular job.

• 4:42Flora Lichtman?

  I mean, there were so many medical and science advances during Agatha Christie's time. Is there any evidence that she was keeping up with this?

• 4:50Speaker 04

  Oh, absolutely. I would say perhaps one of the best examples is her use of bacterial poisons. Bacteria are superb poisoners. They've had millions of years to evolve very deadly, very specific toxins that enable them to live, grow, multiply. And she understood that there was a real threat if someone got an infection and there was a very good chance that they would die. Our ability to fend off bacteria is only really a century old, less really. And Christie wrote about the use of bacteria poisons as a deliberate murder weapon pre-Second World War.

• 5:34Speaker 04

  She didn't use it after the Second World War, probably because she realized that antibiotics gave her victims a very good chance of surviving, which is great for the victim. It's not so good when you're trying to plot a murder mystery.

• 5:47Flora Lichtman?

  Wow. Do you think that the scientific accuracy made the book stronger?

• 5:52Speaker 04

  I think so. And she has no obligation to be scientifically accurate. This is an invented world. She can be as creative, as fictitious as she wants to be. I think most readers will forgive almost anything within a story as long as it follows its own internal logic. But to someone who appreciates how accurate it is, I think it makes it that extra special good. One of her favorite or her most cherished compliments that she received was a review by a pharmaceutical journal that complimented her on the accurate uses of poisons.

• 6:34Flora Lichtman?

  Of all the reviews.

• 6:35Speaker 04

  Of all the reviews, just to say, not whether the story was good or bad, but the use of poisons was accurate.

• 6:43Flora Lichtman?

  In your book, we learn a lot about different poisons. And I was curious about your target audience. Like, are you, are you going for Agatha Christie diehards, chemistry nerds, serial killers?

• 6:57Speaker 04

  In a very selfish way, I'm going for absolutely anybody that wants to buy my book. So I am very-

• 7:03Flora Lichtman?

  Of course, certainly.

• 7:05Speaker 04

  I'm very happy to cater to Agatha Christie fans, science fans. But this is not a how to guide. You are not going to get very far using my book as a method of planning your future murder. So there are key bits of information that are missing. I'm sorry to say, even if you are successful in your murder, you are going to be caught. And it's very difficult to explain why you have this well-thumbed edition of my book on your bookshelves with passages underlined.

• 7:36Flora Lichtman?

  Okay, so why do you think poison captures the imagination? Like, what makes it good for one of these stories?

• 7:43Speaker 04

  It is an incredibly devious method of murder. The idea of poisoning, you have to think about this. You really have to plan it. You can't just lash out with poison. You have to figure out how you're going to obtain it, how you're going to administer it. Also, what you're going to do whilst you're waiting around for it to take effect. So there's a lot of opportunities to think about what you're doing and reconsider. Murderers that use poison, they've got this kind of extra layer of nastiness to their personality, just because they've really thought about this and continued with it.

• 8:20Flora Lichtman?

  What's your favorite poison?

• 8:22Speaker 04

  Oh, it changes all the time.

• 8:26Speaker 04

  Honestly-

• 8:26Flora Lichtman?

  A poison for every, every season?

• 8:29Speaker 04

  A poison for every season, every occasion, every mood. I get asked quite a bit, what poison would you use to kill someone? I'm obviously not going to divulge that publicly, so I have to step around it. And I have to- Explain to people that obviously I would tailor my poison to my victim. Because what you absolutely have to do is avoid the autopsy. The people who do autopsies, forensic toxicologists, they are superb at their job. And they are tenacious in finding those killer substances. Which means you've got to make your murder look like natural causes or an accident. So you're going to have to have a complete medical history, you're looking for pre-existing conditions.

• 9:12Speaker 04

  And you've got to tailor your poisons to produce those symptoms.

• 9:15Flora Lichtman?

  You know, I think there are, people are familiar with nightshade and hemlock and arsenic, but. Are there sort of lesser known poisons that you feel like don't get, don't get the limelight, but really should?

• 9:27Speaker 04

  Don't get the publicity that they really deserve.

• 9:31Speaker 04

  That what I try to get across to lots of people that I talk to about poisons is that poison is just the dose. Literally anything can be a poison if you give someone too much of something. So you can kill someone by giving them too much water. It takes a lot of water, they will notice and try and resist. So most poisons, most things that people think of as poisons are toxic in very small quantities. Having said that, there are all sorts of compounds that are surprisingly toxic. If you take a relatively small amount.

• 10:08Flora Lichtman?

  Such as?

• 10:08Speaker 04

  So one of the ones that, one of the ones I particularly enjoyed researching for this book was nitroglycerin. Because we all know it as an explosive. This is what Alfred Nobel tamed and put into dynamite. This is how Alfred Nobel made his fortune and was able to bequeath these awards. For the betterment of humanity through scientific and endeavors, literature and peace. But this nitroglycerin is also a very good medicine. Because it doesn't just disintegrate very rapidly to cause an explosion. It will disintegrate in the body to release very slowly nitrous oxide. Which dilates your veins and your arteries.

• 10:54Speaker 04

  So if you have a constriction in the arteries feeding into your heart, then it can open them up. So it is a brilliant drug, but obviously if you take too much of it, you can dilate those vessels so much. That you get a catastrophic fall in blood pressure.

• 11:14Flora Lichtman?

  Nowadays, you could not get away with murder using the poisons that Christie did. The science of why? Coming up after the break.

• 11:22Speaker 04

  The poisons that Agatha Christie used, they date her novels as much as the clothes, the conversation, the cars, et cetera, et cetera.

• 11:31Speaker 02

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• 14:02Flora Lichtman?

  Agatha Christie kills off a few people with digitalis.

• 14:05Speaker 04

  Yes.

• 14:06Flora Lichtman?

  And I recognize it from the movie Casino Royale, where Daniel Craig, as James Bond, is playing poker when he realizes his martini was laced.

• 14:17Speaker 04

  Who is it?

• 14:19Speaker 05

  007.

• 14:21Speaker 05

  Bond's been poisoned. He's going into cardiac arrest.

• 14:26Speaker 05

  Stay calm. And don't interrupt, because you'll be dead within two minutes unless you do exactly what I tell you. I'm all ears.

• 14:33Flora Lichtman?

  What is it? What is digitalis?

• 14:35Speaker 04

  So digitalis is, the technical name is a cardiac glycoside. So the cardiac bit is the clue. It affects the heart. There are several compounds within foxgloves that produce an effect on the heart, and several of them have been isolated, purified, and formulated as heart drugs. They slow down heartbeat. So you get slower, more intense contractions of your heart. So if you have a rapid fluttering heartbeat that is not efficiently pumping blood around your body, digitalis can slow that down, coordinate it so the blood moves around your body, delivering oxygen in the way that it needs to. Obviously, if you have too much,

• 15:19Speaker 04

  you can slow down the heart to the point that it stops, or you push it the other way and you disrupt that coordination.

• 15:27Flora Lichtman?

  So Bond's team says he has two minutes to intervene or he'll die. Does digitalis act that fast?

• 15:33Speaker 04

  Yeah, I mean, he does very quickly stagger to the bathroom to vomit and try and get rid of as much poison as possible. But obviously, he doesn't get rid of it all. And he then staggers out to the car park, where he's got a complete medical suite just in the glove box of his car. So it would normally take a little longer to maybe take effect on the body. But this is a fast-paced film. So of course, they speed things up. But ultimately, it's a very quick trip to the morgue if your heart stops beating.

• 16:05Flora Lichtman?

  You know, I have foxglove in my garden.

• 16:07Speaker 04

  Yeah, so do I.

• 16:08Flora Lichtman?

  Is it the very same?

• 16:10Speaker 04

  Yes.

• 16:11Flora Lichtman?

  So could, if I ground up the petals or something like what?

• 16:15Speaker 04

  Oh, don't make tea out of foxglove leaves. No, that's, that's a terrible idea. Don't do that.

• 16:22Flora Lichtman?

  Okay. Are there many antidotes for poison?

• 16:25Speaker 04

  There are quite a few antidotes. There are quite a few poisons that do have very specific antidotes. For example, um, opiates, morphine, heroin, drugs like that, they interact with quite specific receptors. So the antidotes are chemicals that lock into those same receptors that don't activate them. So they literally just push the drug out of the way. So the counteracting of the effects of the drug is almost instant. Uh, it is life-saving for people who have overdosed. So that's a really specific example of an antidote. An awful lot of poisons, however, when you turn up in an emergency ward, they will treat symptoms.

• 17:09Speaker 04

  So if your heart is racing, they will give you a drug that calms your heart. If your heart is slow, they will give you a drug that increases the heart rate. And they will treat symptoms as they present themselves until the body is stabilized. It's about keeping the patient alive and comfortable until the body can naturally break down that poison and get rid of it.

• 17:30Flora Lichtman?

  You're listening to Science Friday from WNYC Studios. We're talking about the science of poison. Happy summer to you with Catherine Harkup. Can you build a tolerance for poison?

• 17:43Speaker 04

  Oh, depends on the poison. So if you're thinking about something like the Dorothy Elseiers story, Strong Poison, where two people eat an arsenic-laced dinner and one person survives and the other person doesn't, because spoiler, they've kind of prepared themselves by eating little doses of arsenic. That won't work. I'm afraid you're, you're both goners. But the science at the time was absolutely spot on. It's just that the science has discovered more. We have moved on.

• 18:12Flora Lichtman?

  Okay, so Agatha Christie died in the seventies. Do you think that murderers could use those same poisons now and get away with it?

• 18:20Speaker 04

  Generally speaking, no. The poisons that Agatha Christie used, they they date her novels as much as the clothes, the conversation, the cars, et cetera, et cetera. Because a lot of the poisons, what we call poisons now, were part of medicine. And this is how she knew about them. But medicine has developed safer alternatives to a lot of these drugs. So you simply can't get hold of the kind of compounds Agatha Christie was dealing with. Secondly, uh, medical care has improved dramatically. So you are more likely to survive if you have been poisoned with some of these substances. And thirdly, forensic detection is also much, much better.

• 19:04Speaker 04

  So you are far less likely to get away with it.

• 19:06Flora Lichtman?

  I want to get into your head a little bit. Are you, having written these books, just constantly scanning the room for suspicious plants? Like, has this infected your outlook?

• 19:17Speaker 04

  Um, I would like to say no.

• 19:25Speaker 04

  There was an occasion where I went to a coffee shop with a friend. And it was a lovely coffee shop that had fresh flowers on top of their little cake display. And I looked at the fresh flowers one day and they had a particularly toxic plant that had been picked and put into a vase. And I very stupidly asked the person behind the counter if they were real or if they were fake. And this particular toxic plant, you can absorb the poison through your skin. And to my shame, she rubbed the leaves with her fingers to confirm that it was a real plant. So I didn't have

• 20:01Flora Lichtman?

  That's on you.

• 20:02Speaker 04

  I I thought twice about where certain flowers end up.

• 20:08Flora Lichtman?

  What's your next book? Are you staying on the murder train?

• 20:10Speaker 04

  I I'm afraid I am stuck on the murder train. The next book I am currently researching and I'm going through the very worst of humanity at the moment. I am writing a book on how to get away with murder or how not to get away with murder.

• 20:27Flora Lichtman?

  Delightful. Catherine, thanks for joining me today.

• 20:29Speaker 04

  Thank you.

• 20:30Flora Lichtman?

  Dr. Catherine Harkup is the author of V is for Venom: Agatha Christie's Chemicals of Death.

• 20:40Flora Lichtman?

  Thanks for listening. Don't forget to rate and review us wherever you listen. It really does help us get the word out and get the show in front of new listeners. Today's episode was produced by Rasha Aridi. I'm Flora Lichtman. Thanks for listening.