[MUSIC] [MUSIC] The element thallium is not as well known as arsenic but it is very, very toxic. It also used to be very widely available because it used to be the standard rat poison, and in some countries around the world, you can still buy thallium compounds to use as rat poisoning. And you can see from this picture, it says, "Thallium, rough on rats". Well, it's not just rough on rats, it's also very rough on people. The lethal dose is about 12 milligrams per kilogram body weight. And it works by interfering with the nervous system, and this is due to a chemical similarity with the element potassium. Unlike arsenic, however, thallium has a particular symptom that is very, very characteristic. And that is, if you're poisoned with thallium, one of the things that will happen is that all of your hair will fall out. This is very characteristic of thallium. One poisoner who used thallium was Graham Young, a very disturbed individual. Graham started his career of poisoning even at the age of 14, when he murdered his stepmother. He was sent not to prison, but to Broadmoor Psychiatric Hospital. This is a secure hospital and the people there are treated as well as detained. There are rumours that he may have poisoned another inmate while he was in Broadmoor, but in 1971, he was considered to be cured and so he was released back into the community. When he was released, he was able to get a job and he got a job working in a warehouse. By an unfortunate coincidence, one of the duties that he had in this warehouse was to make the tea. So it's the perfect job for a would-be poisoner. So, it's believed that he attempted to poison eight of his co-workers using either thallium or antimony. Now, Graham Young doesn't seem to have been interested in killing a lot of people as fast as possible, because he would give relatively low doses for a long time so he could watch the effects and then, presumably, give a higher dose later. The result was that while eight of his co-workers became ill, two of them died. Bob Egle was the first to die and he as cremated. When the second worker died, Fred Biggs, then there was a very serious investigation. It was suggested, in fact it was suggested by Graham Young himself, that this looked like a thallium poisoning. So, the investigators went back and re-investigated Bob Egle's death. Now, remember, he's been cremated, but we're talking about thallium. Thallium is an element, so thallium cannot be destroyed. So they went back to the ashes of the victim. They were able to analyze the ashes and prove the presence of thallium in the ashes. Not only could they show that thallium was present, they could also measure the level of thallium and make a very good estimate of the amount of thallium present and show that it exceeded the legal dose. Well, with this evidence, it led to Graham Young's conviction of the murders. This time, he didn't go to a psychiatric hospital, he was sentenced to life in prison and he died in prison some years later. [SOUND] Rather bizarrely, Graham Young does still have his fans. This is a story from Shizuoka, in Japan, a few years ago, where a 17 year old girl fed thallium to her mother. The lady didn't die, but she was extremely ill. Thalium has some very, very nasty effects. But the judge realized that this girl did not hold a grudge against her mother. She just wanted to do an experiment. But of course, there's a big difference in doing an experiment in a test tube and doing it on a human being.