Molecules and Murder is a new series on the blog, inspired by Professor John Nicholson who studied chemistry at Kingston University. This is the second one of the series and I hope you enjoy.
We left off with: ‘It’s not always obvious whether somebody has been poisoned’. The rate of poison in the UK is 1 per year, so it is quite a rare case over here however, having said that, it is quite difficult to identify if someone has been poisoned.
Some examples of poisons include: Arsenic, Cyanide, Thallium, Aconitine. What do these poisons have in common? Nothing. It is quite difficult to figure out from first principles if a particular chemical is a poison. Cyanide is a functional group (carbon and nitrogen) and cyanide turns out to be in all sorts of molecules including a substance called amygdalin which is in apple pips. So, if you have swallowed an apple pip, you’ve had a little dose of cyanide…
Cyanide is also contained in simple salts e.g. KCN which is exceptionally toxic. There was a case in 2000, John Allan who gave his very wealthy girlfriend potassium cyanide (KCN) during a holiday together. Prior to this, he got her to change her will so he could own the house and sports car she had. John Allan is currently in prison for life in the UK. You can read more about this story here.
The fourth one on the list above: Aconitine which is a compound and is quite an unusual poison. It is a metalloid element and often found in nature, obtained from the Monkshood plant which is quite an attractive garden plant.
The Case of Lakhvir Singh
Aconitine was used by a lady called Lakhvir Singh to kill her former lover in 2009. Ms. Singh had a 16 year long term relationship with Lakhvinder (‘Lucky’) Cheema, however he had broken that relationship for a much younger women, Gurpreet. And so, on the 27th January 2009, both of them became violently ill and eventually died after eating a curry prepared by Lakhvir Singh. In Indian cookery, they actually use the monkshood plant to prepare foods however, it is cooked throughly to remove all the poison. She had got the monkshood plant from India to poison the curry but added it in fresh so the poison wasn’t destroyed. The police had found small packets of the plant’s root found in her coat and bag. This was identified Ms. Singh was arrested on 31st January 2009 and sentenced to life imprisoned.
Arsenic, another poison was also found quite commonly as Arsenic Oxide, also known as white arsenic and in Victorian times, it was used as a household chemical (e.g. weed killer, rat killer, etc.). As much as it were useful, at the same time, Arsenic poisoning was extremely common. Arsenic being group 15 is in the Nitrogen group so it means it can replace N in organic compounds. For example:
The Case of Major Armstrong
In 1921, Major Armstrong had used white arsenic to poison is wife. He originally got away with it. He went down to his local pharmacy and claimed he needed it for his garden to kill the weeds…in February. Shortly after his wife died, a new solicitor moved into his town and he was clearly envious and Major Armstrong invited the solicitor to tea; offered him some cake and felt extremely unwell after this due to the white arsenic. But how was he able to get hold of this arsenic so easily? His father-in-law had been selling white arsenic to Major Armstrong and he was a bit suspicious, so he went to the police; they dug up the body of Mrs. Armstrong and found considerable amounts of Arsenic in her. Finally, he was found guilty and hanged in 1922. He was the only solicitor ever executed for murder in the UK.