Interviews August 02, 2021

By Forensic Access

In the penultimate episode of Lynda La Plante’s Listening to the Dead podcast series, Forensic Access’ expert toxicologist Victoria Jenkins separates fact from fiction in poisoning cases, and discusses how hair, nails and even soils can be used to detect the presence of drugs and other intoxicants.


Unless you had suspicions that a poisoning had occurred, and you were able to give the toxicologist or chemist an idea of what the poison was, poisoning wouldn’t be routinely searched for. Is this still the case?

“Routinely toxicologists would look for alcohol and they would look for commonly-used illegal drugs such as heroin, cocaine etc. The use of more common prescription medication would involve looking for things like antidepressants, but there would always be a range of drugs that won’t be picked up on those tests unless you specifically ask to test for them.

Additionally, tests that would detect the presence of certain gases like carbon monoxide would require different testing. It wouldn’t routinely be picked up on the normal drug screening tests that would be performed.”


Do poisons remain in the cadaver forever? Even when decomposition takes place, would you still be able to detect poisons?

“It depends to some degree on the poison. You have a condition called post-mortem redistribution where after death, because of changes that happen with the pH of the body and the diffusion of substances from tissues into the blood sample, drugs can get redistributed.

“In what we call decomposition fluids, as the body breaks down over time, substances can disappear from the body and those decomposition fluids might leak into the soil. There might be nothing left to analyse after a period of time.”


In that situation, can you analyse the soil? Would there be anything there, or would the poison just dissipate?

“Potentially yes. You would be looking at a relatively significant period of time – I have been involved in cases where there have been body exhumations and there is still some tissue that you could take a sample from. There could also be some decomposition fluid still present, or say if the eyes were still intact there’s a fluid present called aqueous humor which has fairly similar levels of drugs in it to the blood.

“So if a lot of blood has been lost from the body, you can take a sample of that fluid and it will tell you what drugs levels were in the body probably about one hour or two earlier prior to the time of death, because it takes a little bit of time for the drug levels to correspond with the levels in the aqueous humor.

“There’s generally still some way of detecting, up until the point where you’ve just got bones remaining.”


If you’re analysing a body and there has been a case of poisoning, but maybe it didn’t get picked up immediately, where can you look for clues that poisoning has occurred and how long after someone has ingested the poison does it take to register in those areas?

“The best fluid for looking at toxicology, whether somebody is alive or dead, is going to be the blood because the drug level in the blood is what’s circulating around the body and can act on a receptor and cause an effect. So the blood level is always the starting point.

“But there would be cases in extreme trauma or blood loss where there isn’t sufficient blood to analyse. The other options we have are urine – you can take a urine sample from the bladder. Other than that, you can look at tissue samples and you can also look at hair samples.

“Hair can provide a history of somebody’s drug use, but it isn’t particularly helpful if a person has ingested a poison and died soon after. This is because it takes about five to ten days for that hair sample to appear above the scalp, so the hair that can be analysed isn’t going to tell you any information about very recent drug use. But it can sometimes be helpful if someone has been administering drugs over a long period of time – you would be able to detect historic drug in a hair sample.”


Cyanide and arsenic are the classic examples of poisons that you commonly hear about, how often do they come up in your work?

“I’ve not encountered any of what you would call “naturally occurring” poisons being used.

“The cases that I have worked on have involved drug overdoses where you cannot always necessarily tell whether that person has deliberately overdosed or whether another person has deliberately administered the drug to them. They often involve a drug overdose of something that the person routinely takes.”


When you’re testing a hair for example, does dyeing of the hair alter any kind of toxicology result?

“There have been studies looking into the effects of whether somebody’s natural hair colour affects how drugs are taken up into the body, and there is variation between different people to the point where you can’t necessarily say from a drug level in somebody’s hair how much they’ve specifically ingested, or compare it to another sample.

“But by looking at the length of hair it would allow you to tell within the same individual whether there has been an increase or a decrease in the pattern of drug ingestion over time.”


Do toxicologists visit crime scenes?

“Not at all, I’m not even laboratory-based! The lab report comes to me and then I interpret those findings, so once a drug has been found in a blood sample for example, somebody might want to know how long that drug may remain detectable in the blood after ingestion.

“The questions that might also need answering can include whether a person has taken the drug two or three days earlier, whether the drug level present is a therapeutic level or a fatal or toxic level… it’s purely the interpretation side of it and then I only really leave my office to go to court if the findings need further explanation.”


So you have all of these experts doing blood, semen… all the different sections, and then you receive the report and have to go through the report to determine what you think is suspicious?

“That’s correct, and as well as the toxicology report I can request further information. So I can perhaps request somebody’s medical notes to see whether they may have an underlying condition that might make them more susceptible to the effects of a toxin.

“If necessary, I can also ask for witness statements if somebody has been seen after they’ve ingested a drug – so sometimes the cases I work on are surrounding a death where there’s a substance in that person’s blood sample that hasn’t necessarily killed them. It might be that they’ve taken something hallucinogenic and jumped out of the window of a building, and they’ve then had a level of drug in their body at the time. You would then have a look at the witness statements to see how they were behaving beforehand to see whether the drug ingestion had a profound effect – perhaps someone reported them as experiencing hallucinations and something like that has caused them to jump out of a window, off of a bridge or explain the means that they’ve actually died by.”

“Relatively few number of cases that come across my desk are actually to do with overdoses and poisonings. But there’s no way of knowing how that represents what’s going on in society, and if you look at the case of Harold Shipman for example, he murdered around two hundred patients before he came to light. So there could other people who are doing this on a smaller scale, and it sometimes takes for it to reach an excessive number before what’s actually happening rises to the surface.”


Is that an example of an instance where you would need to analyse the hair, because you’ve got a poisoning that’s gradual over a prolonged period of time, and it’s not showing up on any of the other tests?

“Every case is obviously slightly different, but when somebody dies there is a reason why the case has come to me. So there’s been some suspicion aroused, and that could be for a number of different reasons.

“In something like a heroin overdose, if someone is trying to make it look like a person has overdosed themselves, they want everything to look as consistent as possible with the process of them having overdosed. Sometimes it can be as simple as their friends saying ‘she always injected heroin in her groin, she would’ve never injected in her arm’ or ‘she used a specific tourniquet that wasn’t there.’ It will always be something that’s led to suspicion in that respect.

“From the toxicology point of view, you can’t always be certain, even if there’s a fatal level that it has been accidental or deliberate. My report will be taken into context with various other bits of information from the scene, including any eyewitness statements, to form an overall picture of how a death has happened.”


What would you say are the most used poisons?

“Going back through history: mercury, arsenic, thallium… none of them are substances that I would come across today. But they have been used historically, and hemlock is also another example of a historic poison.

“But nowadays as I say, if someone is trying to poison another person, it tends to be with a medication that the person is prescribed anyway. Then it potentially would look less obvious if that drug showed up in their blood sample.”


Munchausen cases are quite common, whereby a child is consistently proven to be sick and then the parent is accused of purposefully poisoning the child. What is the usual method that would be used in a Munchausen case?

“Again, it tends to be a medication that’s in the house, even if it’s a medication that the child hasn’t been prescribed. There tends to be an argument that the child has accidentally ingested it by picking it up themselves. So it would usually be a sedative medication that’s available within the house.”


What sort of cases have been coming across your desk in the past five years?

“I probably work on around five cases per year involving poisoning. My main workload is in relation to driving offences. In 2015 there were drug driving limits introduced in the UK, and there’s been a lot of work involved in cases of people driving under the influence of cocaine, cannabis and various different drugs.

“Other types of cases I get involved in are child custody cases and sports testing – for things like the Olympics to see if someone has taken a banned substance like steroids and amphetamines. Because these lists are only updated every now and then, there might be a substance in somebody’s system that isn’t on the banned list, but I’m asked to comment on whether it has any performance enhancing effect.

“Steroids and amphetamines are the main drugs that people would take to enhance their performance, but there may be something outside of those categories that turns up in a person’s urine sample, and I’m ask to comment on whether there’s any way that substance could’ve given them enhanced performance.

“Prison testing is another thing that I get involved in. This includes prisons wanting to monitor if drugs are getting into the facility, so the police will conduct random testing on inmates and I’m asked to remark on whether anything that’s found could be there through medication that the inmates have been given whilst in prison, or whether it is deliberate ingestion of a controlled substance.”


How long would performance enhancing drugs stay in the system for?

“The way those drugs are metabolised, they have a half-life. So if a drug’s half-life is one hour, for example, that means that the drug’s level in the body will fall every hour. That means an hour after it has been ingested its half its original level, two hours later one quarter its original level and so forth.

“Every drug has a different half-life, but in general terms it takes about five to six half-lives for a drug to be eliminated from the blood. For cocaine, the half-life is an hour and it can be detected for a relatively short period of time in blood.

“Some drugs have half lives of two or three days, so they would show up for a lot longer. It all depends on the drug.”


That’s quite relevant to GHB I would imagine. Because it decimates so quickly, one of the problems with a victim coming forward a day or so later is that they only take a small urine sample so no traces of the substance could be detected. Is there a need to make people more aware of that fact, should a person fall victim to a date-rape drugging?

“The trouble if someone is given a drug like GHB, which is essentially a date-rape drug, it sedates them for quite a long period of time so obviously it is going to be metabolised throughout that period.

“There’s then a further period before they get to a police station or some other facility to have a sample taken, so you’re right that would have passed out their system by the time a sample could be taken. It would be beneficial for a person to even just put a sample in a jar at home, so they have something that could potentially prove they have been drugged.”


If someone has ingested a poison, what are the timelines within which it will show up in different parts of your body?

“How quickly somebody shows the effect of a poison will depend to some degree on how it’s ingested.

“Sometimes you see on crime dramas that somebody takes a drink with something in and they drop dead the next second – that’s not realistic at all because if something is taken orally it needs to be absorbed into the bloodstream to have an effect. So it would generally take around thirty minutes for any drug that’s ingested orally to enter the blood stream and take effect.

“Whereas if it were injected, it would enter the blood stream straight away. How long it remains in your blood stream is dependent on its half-life. The majority of drugs you would be able to detect in the blood stream for around twenty-four hours afterwards, and some for significantly longer.

“But there will be drugs like GHB that won’t even be detected for that long after ingestion, they will leave your system much quicker.

“With urine, just because it’s a smaller volume of liquid, the drug becomes more concentrated in the urine. The fact that urine stays in your bladder for some time means that it would retain the drug for a longer period than blood would. It’s usually around two to three days when you would be able to detect the presence of a drug in a urine sample.

“With hair, it’s largely dependent on the length of the person’s hair. Hair grows at a rate of roughly one centimetre per month, so for somebody who has a twelve-centimetre section of hair you could look at their drug history over a period of a year by looking at one end of the hair to another. You can then see when during that year they might have been exposed to a particular drug.

“As well as hair samples, another method of looking at historical use of drugs can include fingernails and toenails. This is because they also have a blood supply going to them, and drugs can be taken up into those tissues as they grow as well. This is useful in cases where someone is bald or recently shaved their head.”


What physical indicators are there that someone has ingested a poison or other drugs?

“A lot of them would have very similar effects – nausea, vomiting – sweating is also quite a common thing that happens after overdose of a drug.

“It’s not necessarily something that will give you a definitive answer to what someone has ingested just by looking at them, but the pupils of the eye are quite a good indicator of certain drug groups.

“Anything that’s a stimulant, such as cocaine and amphetamines, tend to cause dilation of a person’s pupils. Whereas the opiate group of drugs, such as morphine and heroin, tend to cause constriction of pupils. If someone seems a person in the time between them taking the overdose and dying and has observed some of the visible effects like that, it might give an indication as to what group of drugs they have ingested.”


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Listen to the podcast here: ‎Listening to the Dead - Forensics uncovered: S2 E5. Cause of Death – Poisoning on Apple Podcasts