Friday, September 18, 2009


I'd like to know if there's any such thing as an undetectable poison, and if so, what it is. Killing a character this way appeals to me, but everything I've looked at so far, even liquid nicotine, seems to leave some trace that labs can pick up. Also, how do poisons kill, exactly? The corrosive ones I understand-- eat out your organs and you die--but others seem to be applied in such small amounts. How does such a small amount cause such huge damage?

Good Lord, child, I’d have to have a degree in biochemistry to answer that!

As far as I know—and we’d probably all know because mystery writers would use it in every book—there is no truly undetectable poison. There are, however, poisons that might not be detected. Only your killer can decide if that’s good enough for their peace of mind.

The average autopsy will check for alcohol, narcotics and illegal drugs. That’s all. The average crime lab will not have the equipment or reagents to check for every possible poison, so an investigator would have to know what they are looking for. If they do, and there is not currently a way to detect it, a way might then be found.

That’s what happened when David Davis supposedly killed his wife Shannon with succinylcholine. It instantly breaks down into succinic acid and choline, which are normally found in the body anyway. At the time there was no way to detect suspicious levels. A doctor at the Medical College of Ohio, continuing work begun in Sweden, devised a test to do so. Davis was convicted (after going on the lam for seven years) but using a brand-new technique in a criminal trial is always a risky proposition, and the accuracy of it is still under debate. Juries—and everyone else—likes their forensic science to have lots of studies and decades of time behind it before they vote to convict.

The trick is to make the poison fit so perfectly into the victim’s situation that, even if found, it will not necessarily scream murder. Genene Ann Jones killed numerous infants in her pediatric ICU unit by overdosing them with the blood thinner heparin. But these victims were in grave trouble already, so her activities went undetected for far too long.

Dr. John Hill supposedly killed his wife by poisoning pastries with bacteria so that her death would look like a case of meningitis. It might have worked had his behavior not raised so much suspicion. This method would require a good working knowledge of, and access to, bacteria and runs great risk of not working or not working completely. On the plus side, it wouldn’t look like poison, and one could always try again.

But just because a poison is well known doesn’t mean you can’t get away with it. An older lady killing off her husband is the first thing you think of with the word arsenic, but Audrey Marie Hilley did exactly that, while her husband was in the hospital under the care of an army of competent doctors and nurses.

Poisons are difficult to work with because of the variety of behavior and mechanisms. If you shoot someone, a bullet comes out of the end of the gun and flies in a straight line until it hits something. No matter what gun or what bullet you use, that’s more or less what happens. Poisons are a whole ‘nother scenario.

Poisons can work by tying up something that’s supposed to be working—cyanide stops the ATP cycle in mitochondria and robs the body of energy, breaking the chain that allows cells to get oxygen so that you suffocate about as quickly as you would if someone held a pillow over your face. Mercury and ricin similarly interrupt the cellular processes, only more slowly. Potassium chloride takes away the cell potential (electrical charge) necessary to get the heart to beat. Nerve gases block an enzyme that transfers messages from the nerves to the organs. Methanol is a poison that isn’t poisonous at all, until it breaks down to formaldehyde and formic acid in the liver.

They work so quickly because blood circulates completely through the body about every 60 seconds. So some poisons really can kill more or less instantly.

I can tell you one thing—if you want to know how to kill someone without leaving a physical mark or trace, read my book Evidence of Murder. That’s exactly the question my heroine Theresa has to resolve and yes, there is an answer, and yes, it’s completely true. But it’s not poison. Well, not exactly.

Lisa Black spent the happiest five years of her life in a morgue. Strange, perhaps, but true. In her job as a forensic scientist she analyzed gunshot residue on hands and clothing, hairs, fibers, paint, glass, DNA, blood and many other forms of trace evidence, as well as crime scenes. Now she’s a latent print examiner and CSI in Florida, working with fingerprints and crime scenes. She has been published in Germany, the Netherlands, France, the UK, Spain and Japan.


CJ Lyons said...

Hah! Thanks, Lisa for giving us a blueprint to a traceless murder, hehehe....

Jen Forbus said...

O.k. Kelli, we need to keep our Whiskey Sours away from Shane - you don't know what he might try to slip in there in the name of research! ;)

Lisa, for not having that degree in biochemistry, that's a pretty detailed answer! Thanks for the fun.

And when you're all done reading here, come check out Kelli's interview (Part I) over at my place:

Shane Gericke said...

Thank you for the "poisonous" answers, Lisa. You're so very good at this.

Kelli Stanley said...

LOL, Jen, I agree ... we don't want to wind up as experiments in Shane's diabolical research scheme! ;)

I find it fascinating that juries seem to distrust clinical science but trust a gut instinct about behavior. You know, the whole pyschopathic "your wife's missing and you just sold her car" thing that helped convict Scott Peterson.

Behavior seems to be the most damning evidence of all!


Rebecca Cantrell said...

Thanks, Lisa. I like that bacteria idea. Maybe that's just because I'm off of pastries right now.

Love the chatty style and detailed answers you've been giving us all week too! Come back any time. Please.

Unknown said...

Reading your answers all week has been very informative and very entertaining! Can't wait to read your book!

Kelli, I think juries distrust *new* forensic methods. They love tried&true (fingerprint, DNA).

Peterson's girlfriend and the flat affect, were important factors according to the jurors after the trial. But so was the simple fact that he was her husband -- one juror (the crazy died-hair lady) said that he should have protected her -- in other words, the fact that she was dead meant he did it. Which is very, very, very scary logic.

I'm hoping she was just expressing herself badly.

I'm still fascinated by the process of deciding that the solution, the best, the easiest solution to your problems is to kill someone. Short of abuse/starvation type scenarios, I always wonder "what were they thinking!"

Shane Gericke said...

Juries like anything they've seen on CSI, even if it's not true, and wonder why the forensic scientist doesn't wear high heels and bring high-tech laser guided blood spatter systems into the courtroom. When life imitates television. Sigh.

Hey, Lisa, what color does a body turn immediately after expiring. Blue? Gray? A lovely shade of ... something? I've always wondered, and should have asked in addition to my poison questions.

Lisa Black said...

Immediately after expiring? They look a little pale, though whatever part of the body is closest to the ground will be a blotchy dusty rose from the pooling of blood (lividity). After a day, this might take on a slight light gray cast. After another day the skin starts to 'marble', during which the veins turn very dark but the skin is still pale, hence the marble effect. After a couple days in a cool climate, maybe only a day or two in a hot climate, the body will become decomposed enough to turn purple and bloated.