The Myth of the Untraceable Poison
of the most common questions I get from writers is: Is there
a poison that can’t be found in a corpse? The answer is
No. And Yes.
on the state of the corpse when it is found. If severely decayed
or completely skeletonized, the ME and the forensic toxicologist
have their hands tied. Mostly. There are some toxins, such as
the heavy metals (Mercury, Lead, and Arsenic are common ones),
that can be found in bones and hair. But most toxins can’t
be found in corpses that are severely decayed or simply bones.
In a more
or less intact body, your villain can still get away with the
murder by poison. That is, until your clever sleuth figures out
that something is amiss and solves the crime.
thing your murderer must consider is how to make the poisoning
look like something else. An example would be an elderly person
with heart and lung disease who dies in his sleep. In this case,
the person's private physician would sign the death certificate
as a natural cardiac death and the almost always the ME will
accept it. Why? Because there is an old adage in medicine that
says: Common things occur commonly. Most people who die in this
situation do indeed die from natural causes so searching for
something more sinister would be neither logical nor practical.
If the ME accepted the private physician’s cause
of death, no autopsy would be done and no toxicological examinations
would be undertaken. An overdose of Morphine or digitalis or
arsenic or anything else would go undetected.
asked questions. Maybe a high-dollar inheritance or insurance
policy is in play. If an inheritance, one family member could
suspect another and ask questions. In the case of a large insurance
policy, the insurance company would look under every stone before
paying off the policy. Or your sleuth could have some reason
to suspect that things are not as they seem. In any of these
situations, the ME might be moved to open a file and investigate.
But if your
killer is cleaver, he might be able to keep the ME completely
out of the picture or at least give him an easy answer for the
cause of death. If no murder is suspected, he'll take the path
of least resistance, which is also the cheapest route. Remember,
he must live with and justify his budget annually. If he is wasteful
he'll be looking for a job. So, give him a cheap and easy out.
Your sleuth will then have to battle the ME to get the case re-opened.
thing a clever poisoner can do is to use a poison that is not
readily detectable and will slip through most drug screens. Toxicology
testing follows a two-tiered approach. Screening Tests, which
are easier, faster, and cheaper, are used to identify common
classes of drugs such as narcotics or amphetamines. This only
tells the ME and toxicologist that some type of narcotic or amphetamine
is present, but not which one. Determining which one requires
more sophisticated, time-consuming, and expensive Confirmatory
Testing. And if the screening tests are normal, no further testing
is warranted and the ME would not spend the time and money to
go further down that road.
typically test for alcohol, narcotics, sedatives, marijuana,
cocaine, amphetamines, and aspirin. Some screen for a few other
classes. Once a member of a class is identified, then confirmatory
testing will determine exactly which member of the class is present
and in what amount. For example, if narcotic is found in the
screen, further testing might show that the actual narcotic present
is morphine. Or an amphetamine might be further analyzed and
this might show that methamphetamine is the culprit.
could use a poison that would not be found in the typical screen.
Things such as arsenic, selenium, and most plants (oleander,
deadly nightshade, etc.) do not show up on the typical tox screen
and when the screen came back negative, the ME might not go further.
Why would he spend the time and money without a good reason?
This is where your sleuth steps in to shake things up.
a poison is suspected and if the funds and interest to pursue
it are present, anything can be found in an intact corpse. Using
gas chromatography in conjunction with either mass spectrometry
(GS/MS) or infrared spectroscopy (GC/IR) will give a chemical
fingerprint for any molecule. And since each molecule has its
own structure and thus its own fingerprint, every compound can
be distinguished from every other one.
a good mystery that will keep the reader guessing to the end,
you must plot the nearly perfect murder. This way when your sleuth
cracks the case, he or she will be a true hero. If poisoning
is your killer’s chosen weapon,
then use the above principles to make your plot as clever and
convoluted as possible. Have your killer mask the death as natural
or use some poison that is not readily detectable in screening
tests and then your sleuth must be very clever to solve the case.
several sources for you to search out poisons and to discover
how they act and how they are identified. Google, of course,
and try plugging into your state poison control center. My books, Forensic For Dummies, Murder and
Mayhem, and Forensics and Fiction cover a number
of poisons. I also recommend Howdunnit: Book of Poisons by
Serita Stevens and Anne Bannon fro Writers’ Digest Books.
It is a great resource for poisons of all types.
D.P. Lyle, MD