Is there a perfect poison?

09 January 2018

Interview with 

Dr Lorna Nisbet, Anglia Ruskin University, Dr John Emsley, chemist and author

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The poisons we’ve discussed so far are, thankfully, all detectable, and there are things we can do to reduce the risk of accidental poisoning. So where does this all leave our search for the perfect poison? Katie Haylor asked John Emsley...

John - I don’t think there is one now. Because of high performance liquid chromatography, which can separate every component of a mixture, along with mass spectrometry, which can identify anythings that's present, there’s no way once you suspect somebody’s died of poison, even a tiny strand of their hair analysed by this technique will reveal what it is. That’s assuming that a little of the poison has gone into the hair which often it does.

There’s no such thing any more as the perfect poison. Even something like adrenaline, which looked to be a perfect poison for this awful women in America. She had to use so much of it she needed to do that in order to wreck the heart as it were and, of course, once that person’s died there’s a residue of this at a higher level than nature can provide. So I just don’t think there is such a thing now as a perfect poison.

Katie - Good news! Reassuringly, John thinks there’s very little chance of a poison being able to escape our modern detection methods once a poisoning case is suspected. But, it’s one thing to have the benefit of history and hindsight looking at compounds we know and understand. What about new compounds? According to The Office for National Statistics deaths from new psychoactive substances are on the rise. Here’s Lorna again...

Lorna - If I’m going to stand up in court and put to a pathologist “this my toxicology report, this is what I have found”, I have to be confident that I have found what I’m saying I’ve found. In order to do that I have to have a reference standard or I have to have a copy of what is called its mass spectra in a library. You can’t compare an unknown and magically know what it is. You’re comparing your unknown with a known. If I do not have a reference standard or a spectra of some sort to compare, I cannot go into court and argue that that is definitely what it is.

Katie - Compound to compound, you cannot guarantee that is the same?

Lorna - No. You would have to able to compare a known, and an unknown so that you can say that this is what this definitely is and you have to be able to prove the evidence for that. If these reference standards and if these spectra have not been done for that compound yet, so for instance, some of the psychoactive substances, we’re struggling to keep up with them. About two a week come into Europe right now so, realistically, we have more new psychoactive substances around than we do have of the classical drugs, so that can become a bit ‘needle in a haystack.’

Katie - In terms of poisons, I’m assuming people don’t take psychoactive drugs because they want to poison themselves, they take them for their intended effects. Can a psychoactive substance be a poison?

Lorna - Yes, it can. But it depends on the side effects of that psychoactive substance. The toxicity is what you’re looking for, normally with really classic drugs we would do LD50, these are what it takes to kill 50% of a population. Some of these drugs have a very high LD50s or they’re just unknown completely. LSD, for instance, most of the deaths from LSD come because, unfortunately, someone has fallen from a building. It’s through a mechanical death rather than the actual drug. But the newer versions of them, which are called n-bombs are much, much more potent and you don’t need the same amount. The onset of them is slightly slower so people tend to redose and, unfortunately, that’s how they die.

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