THE FOLLOWING ARTICLE APPEARED IN THE

OCTOBER 1997 ISSUE

THE POISON SLEUTHS

POISONING BY THALLIUM

-Dr. Anil Aggrawal

"Good morning doctor. Oh, my God, what are you doing today. You seem to be doing the post-mortem on a rather old man. And he seems to have a most peculiar rash over his face. His hair have also come off his head. Please tell me what happened to him."

"Good morning Tarun. This man is a 56-year old man Ramlal, who worked in a store in New Delhi. He suddenly fell ill on 27 August. He developed acute griping pain in the stomach for about 1 hour, and he also had vomiting and diarrhoea. He was well until four days later when he developed severe burning pain in the toes of both feet and tingling sensation in the tips of all the fingers. These symptoms increased over the next five days with some reduction in the power of hand grip. His company admitted him to a leading private nursing home in Delhi. Some leading medical experts examined him, but couldn't diagnose his illness. Ramlal's condition remained unchanged until 9 September when he suddenly developed more symptoms. He had difficulty opening the eyes in strong light, a symptom known in medical parlance as photophobia. There was some disturbance in his vision also. His condition worsened further over the next few days and by 11 September there was drooping of eyelids (known in medical parlance as ptosis) and weakness of face muscles. Swallowing became increasingly difficult. He had difficulty in breathing too, which became so severe that on 15 September, a surgical opening had to made in his neck to help him breathe. However his condition continued to worsen and he died on 19 September, 23 days after his first symptoms started."

"Oh, he had a most terrible illness. What do you think he died of?"

"Everybody thought he had died from some undiagnosed natural illness. But when the dead body was brought to me, I noticed this curious rash over his face. I also noticed- as you also did- that his hair were also falling off his scalp. This made me suspect that Ramlal was being poisoned- perhaps with thallium."

"What! Thallium!! I never thought that it could be used as a homicidal poison"

"Tarun, on the contrary, it is a very good homicidal poison. I will tell you in a short while, why this is so. But before proceeding any further, let me tell you a little bit about thallium, so that you can know something about this interesting poison.

"Sure doctor, go ahead. I like listening to good scientific stories."

" Tarun, Thallium was discovered in 1861 by the British physicist Sir William Crookes (1832-1919). He was working with selenium ores, and in 1861 he came upon a sample of such ore that when heated showed in its spectrum a bright green line characteristic of no known element. It indicated a new hitherto undiscovered element. When he ultimately found it, he named it thallium, from the Greek word thallos meaning "green twig" after the color of its line. The botanical word thallophyta comes from the same root."

"That's very interesting. And when did murderers start using it as a homicidal poison?"

"It is significant that it was not used as a poison in the first instance. Its earliest use - albeit unaccountably- was to check the "night sweats" in tuberculosis, and when it was noticed that loss of hair occurred with its use, a scientist named Sabouraud instituted its therapeutic use for tinea capitis or ringworm in 1898. The salt used was thallium acetate. It was supplied as a cream (Koremlou cream), containing 7.18% thallium acetate. This practice was finally abandoned half a century later, when it was realized that it was a potential poison. Quite interestingly Thallium has also been used a rodenticide (e.g. to kill rats and moles) and as cockroach poison, particularly in Germany. For this purpose it was available either as tablets or pellets of thallium sulphate or as pastes. Some time in the 1920s the firm of Bayer-Leverkusen in Germany marketed 30 g tubes of a paste known as Zelio paste, each of which contained 2.3%, or about 600-700 mg of thallium sulphate. It had a wide sale on the continent and in the United States, apparently without any restriction of sale or purchase. A French preparation, Virus Rouge contained thallium nitrate. In 1965, the US banned the use of thallium as a commercial rodenticide. However thallium salts as cockroach poison may still be available today in many countries. It is still used in homeopathic remedies!"

"Doctor, why did anyone use thallium as a rodenticide at all, when it was so dangerous to human beings?"

"Tarun, the earlier rodenticides contained phosphorus, but the value of thallium as a rodenticide lay in the fact that the usual phosphorus containing rat-killer was harmful to the pigs that ate the poisoned rats, whereas the pigs seemed unaffected by rats killed with thallium salts! The use of thallium rodenticides in Europe spread when the Germans conquered and occupied most of Europe during the 2nd World War."

"Is thallium useful for other purposes too?"

"Yes, Thallium is widely used in industry. Its addition confers a high refractive index on optical glass. For this reason it is used in imitation jewellery which sparkles rather like diamonds. It is also used as an alloy, a catalyst, and for making low-temperature thermometers. But unfortunately like arsenic (see Science Reporter February 1997) , thallium also accumulates slowly in tissues, and over a short period of time, has cumulative toxicity. This method of administration has been used in many criminal cases. I must tell you that the fatal dose of thallium is about 1 g."

"Excuse me doctor, what do we mean by the fatal dose?"

"When dealing with poisons, we often speak of their fatal dose and fatal period. You will perhaps remember that we first talked about the concept of fatal dose, while talking about arsenic and Spanish Fly (see Science Reporter February 1997 & March 1997). Fatal dose of a poison is the average dose which is enough to kill an adult human being, while fatal period is the average period taken by the poison to kill. A tube of Zelio paste would contain about 0.6 to 0.7 g of thallium which is considered somewhat less than the average dose to kill a human being. Death usually occurs in 11 to 16 days, which is called the fatal period of thallium. If the patient survives 4 to 5 weeks, he would probably live, but the damage to organ systems may be permanent."

"Tell me doctor, can thallium be taken for suicidal purposes too?"

"Tarun, cases of both accidental and suicidal poisoning occur with thallium, but probably most sinister is its use as a homicidal poison, as it possesses many of the qualities of an ideal homicidal poison. Its salts are colorless, odorless and tasteless, besides being freely soluble in water. Furthermore, in the body the salts are converted into a relatively insoluble salt thallium chloride. This is favorable to the criminal, as the insoluble salts take longer to act; the effects are rarely noticeable before 12 hours and may be delayed as long as 48 hours. This gives the criminal enough time to cover its tracks. Because of the wide gap between ingestion and the onset of symptoms, it is also that much more difficult to associate the symptoms with what the criminal gave to the victim. The initial symptoms of an ideal homicidal poison must mimic some natural disease, and that's exactly what happens with thallium salts too; its initial symptoms are those of a digestive upset of a non-specific character. More specific neurological symptoms occur only after about 2 to 5 days, but still they are very difficult to differentiate from some neurological diseases such as Guillain-Barré syndrome. That is probably why the doctors were at a loss to diagnose thallium poisoning in the case of Ramlal. One of the most characteristic signs of thallium poisoning- gross loss of hair- does not appear until almost a fortnight has passed."

"Excuse me doctor, you introduced quite a frightening term Guillain-Barré syndrome. I know I may be deviating from the main topic, but please let me know something about it."

"Tarun, the actual name of this condition is Landry-Guillain-Barré Syndrome or LGBS. It is the name given to the conditions previously known by two different names- Landry's ascending paralysis and Guillain-Barré Syndrome. Now the two conditions are known to be identical. It is an acute disease of the nerves, in which they lose their outer protective covering or myelin. This myelin coat is also important for the smooth functioning of the nerves. The result of this loss of myelin coat is that the nerves can not conduct messages properly. This disease occurs at a rate of one case per million population per month. At this rate about 950 new cases of LGBS must be occurring in India every month. The weight of evidence favors that the cause of the disease may be immune related. However in over two-thirds of the cases, a viral infection is associated. After the infection, demyelination- or loss of myelin coat- in spinal and peripheral nerves occur. The symptoms of thallium poisoning may mimic this disease very much. The good news about LGBS is that its prognosis is good, with about 85% of the patients making a complete recovery. The mortality rate is just 3-4%. You would probably want to know, how the name of the disease came about. Well, it comes from the names of three doctors who described this disease at different intervals. The earliest to describe it was the Paris physician Jean Baptiste Landry (b. 1826). Subsequently Paris neurologist Georges Guillain (b. 1876) and Strasbourg neurologist Jean Alexander Barré (b. 1880) also described it correctly."

"Excellent. Coming back to thallium. You said thallium fulfills many of the properties of an ideal homicidal poison. It means killers have got an ideal weapon, isn't it?"

"Not exactly. Fortunately nature has put some negative qualities in it too. Had it not been for these counterbalancing features, thallium would indeed have been a poisoner's delight."

"Really? And what are these counterbalancing features?"

"An ideal homicidal poison must not be readily detectable by analysis, but thallium salts can be readily detected. Furthermore, an ideal homicidal poison must disappear from the body after doing its job. Of course a substance can not magically disappear from the body, but what it effectively means is that the poison must at least be destroyed by putrefaction, so that with the onset of time, it becomes impossible to detect that poison. I must tell you that this does happen with most vegetable poisons. Thallium however remains in the body even after putrefaction. It is also not a product of putrefaction."

"Wait a minute doctor. You just said that thallium is not a product of putrefaction. You imply that if a poison is a product of putrefaction, it would be an ideal homicidal poison. Please explain this point to me in some detail."

"Tarun, first of all you must know what exactly is meant by putrefaction. It is the destruction of the body with the onset of time. You must have noticed that dead animals start to rot after some time. The same happens with human bodies, if they are not disposed of properly. This rotting is known as putrefaction in medical parlance. Now imagine a killer has killed his victim with some poison, and has hidden the body somewhere, say in some bushes or a nallah. With the onset of time, putrefaction would start and the body would start to smell. This would soon lead to its discovery. Now if the poison is such that it is destroyed by putrefaction, the doctor doing the autopsy at this time would not be able to find this poison, and thus the killer would remain untraced. Wouldn't it make an ideal homicidal poison?"

"Yes, I do appreciate that. But how can a poison be an ideal homicidal poison, if it is a product of putrefaction? That is what I really want to know."

"Tarun, putrefaction is a chemical process, in which many chemicals are destroyed and many new chemicals appear. For instance, the chemicals skatol and indole are produced during putrefaction which indeed are responsible for the offensive smell of the body. If a poison is a known product of putrefaction, it could reasonably be argued by the defence in a court of law, that the detected poison (in a putrefied body) was not administered during life but was produced as a result of putrefaction. Cyanide, alcohol and ptomaines are well-known poisons which are products of putrefaction. Arsenic and thallium, which otherwise fulfil several of the criteria of an ideal homicidal poison do not fulfil this criteria. Similarly another criteria of an ideal homicidal poison is that it should normally be present in the soil."

"Well, what is the explanation for that?"

"In some communities, instead of cremation, the dead bodies are buried. Poisoners - and in fact all murderers- don't feel easy with this method of disposal of the body, because the potential evidence of murder -the body- remains beneath the soil. Any time after the burial of the body, if suspicion gathers momentum against the murderer, the body can be exhumed, i.e. unearthed and sent for a post-mortem examination. Now if a poison is normally present in the soil, it can be -and has successfully been- argued by the defence that the detected amount of poison had leached in the body from the surrounding soil. Arsenic - a deadly poison- is normally present in the soil in fairly good concentration, and this argument has successfully been used by many murders. But thallium is not present in the soil in any great quantity, and thus the same argument would not hold, if the poisoner had used thallium to dispose of his victim."

"Oh, I see. Doctor, can you tell me what symptoms does the victim experience when thallium is given to him?"

"Yes sure. Thallium salts irritate the stomach and intestines. It is a gastro-intestinal irritant so to say and that's why symptoms like abdominal colic, nausea, vomiting, diarrhoea occur first. Vomiting and diarrhoea may contain blood. There may be sores in the mouth, a symptom known in the medical parlance as stomatitis. The interesting difference from those of other irritant poisons is that the symptoms start very late- after about 24 to 48 hours of ingestion. In fact it is one of the idiosyncrasies of this poison which makes it a good homicidal poison. Thallium appears to act on nerves too. The symptoms relating to nerves ensue one to five or more days after ingestion. An intense pain develops in the body which is worse at night and is readily provoked by mild stimuli. For instance, even the weight of the bedclothing is enough to induce bouts of pain. The soles of the feet are first involved. The pain gradually travels upwards; to the legs and to the trunk. Sometimes there is intense pain in the big toe, and this can simulate gout. In some cases this may be the first sign. Joint pains which move from joint to joint also occur. There is numbness, especially of the fingers and toes, with detectable loss of sensation to pin-prick and to touch. There is a feeling of tiredness in the legs. This is followed by weakness and finally paralysis. The arms are always less affected. An interesting symptom is the appearance of a "butterfly" rash on the face. In fact this is the first thing I noticed on Ramlal's face, and that had alerted me at once. Another interesting symptom is alopecia or loss of hair. In fact it is highly characteristic of thallium poisoning. Hair loss occurs about a fortnight after the ingestion. The hair is lost in large tufts and within three weeks, the whole of head is bare. The root of the hair -the part of hair that remains buried underneath the skin- shows dense black coloration. This may be seen on the actual hair too, if there has been repeated intake. In fact, if there has been a repeated but interrupted intake, several dark bands coinciding with the period of intake may be seen. Interestingly the same thing happens in arsenic poisoning. It is widely thought that the great Napoleon was killed by the British in this manner. His hair too showed arsenic in bands. The bands are seen only on growing hairs. Thallium finally arrests hair growth and the hair falls. Even you noticed both the rash and the loss of hair, as soon as you entered the post-mortem room. During the autopsy I pulled some of his remaining hair and saw them under the microscope. I was struck with the finding that the hair root was completely black, while normally it is not so. The excessive blackness is considered to be due to an excess of melanin laid down through catalytic action by thallium."

"Oh, I see. Coming to think of hair, I find that Ramlal's eyebrows look a little bit curious. Am I right?"

"Yes, you sure are right Tarun. Just like hair on the scalp, eyebrows are also involved in thallium poisoning, but for some curious reason, their inner third is spared- only the outer two-third falls off. It is such a characteristic sign of thallium poisoning that it has even been accorded a name; the sign is called signe de sourcil. This is a French term, which literally means "The eyebrow sign"! It has been suggested that the inner third is spared because it is phylogenetically much older than the rest of the eyebrow hair. The fingernails may bear horizontal white bands or white cross lines. This change appears quite late- several weeks after the exposure. That's why you can't see this change in Ramlal's body."

"Oh, this is most interesting indeed. Especially the information on eyebrows."

"Tarun, there are more interesting nuggets I can give you. You would perhaps be quite interested to know that the noted English crime writer Agatha Christie has given a graphic description of the effects of thallium poisoning in her novel The Pale Horse (Christie, 1952), and this has led a nurse to correctly diagnose a case of thallium poisoning, which had earlier been diagnosed as a case of encephalitis by "experts"."

"Really? Please tell me the details of this case"

"Tarun, this case occurred in the late 70s. A 19-month-old girl in Qatar was having undiagnosed and unexplained ataxia, which in plain and simple terms means that she was unable to walk. Her physician in Qatar telephonically contacted experts in Hammersmith Hospital, London for help. She had a most extraordinary illness. It apparently began some 10 days earlier with a major convulsion lasting about 5 minutes and associated with a high fever. Over the next 3 days she became increasingly clumsy and lethargic and developed slurring of her speech. By the seventh day of her illness she was unable to sit, stand or walk, and had difficulty with swallowing. The following day she had a further generalized convulsion lasting about 5 minutes. At this stage she was transferred to Hammersmith Hospital. Detailed investigations led experts to believe she was suffering from encephalitis -an infection of the brain- but a staff nurse, who was reading Christie's novel The Pale Horse, realized that her symptoms were remarkably similar to those of thallium poisoning mentioned in the novel! The girl had also started losing hair which normally occurs in about 10-15 days of ingestion- a fact which was also mentioned in the book. She expressed her doubt to the doctors and on subsequent examination, she was indeed found to be suffering from thallium poisoning. On detailed discussion with the child's parents it seemed that the most likely source of thallium was domestic poison used to eliminate cockroaches and rodents in the drains and septic tank of their home. This is a common practice in Middle East!"

"Oh, how very interesting. Has Thallium been used for murder in modern times?

"Oh yes, it has. One of the most famous cases of murder with Thallium in modern times is that committed by George Trepal - a 42-year-old computer programmer - in 1988. He was a man with a very high I.Q. In fact he was a member of the high I.Q. club Mensa and this case later became famous as the Mensa Murder case. Trepal lived in the small central Florida town of Alturas. He was quite fed up with his neighbor Peggy Carr, 41, and her family, because they always listened to loud music which disturbed him. Carrs' dogs also used to trouble Trepal's cats, which he did not like. In June 1988, he sent the Carr family a chilling typewritten note in the mail. It said, 'You and all your so-called family have two weeks to move out of Florida forever or else you will die. This is no joke.' Carr's family did not pay much attention to this note. Four months later - in October 1988 - Peggy Carr was hospitalized with mysterious symptoms her doctors couldn't explain. At the same time, her son and stepson developed similar symptoms. While they recovered, Peggy did not, and she died with her doctors still mystified as to what killed her. One of her sons was permanently disabled. Officials were completely baffled. Trepal had actually surreptitiously spiked eight-pack of Coca-Cola bottles with thallium nitrate, and secreted them into Carrs' kitchen. Peggy Carr and her family members unsuspectingly consumed the drink. Peggy lapsed into a three-month coma and died thereafter. Four other members of her family were poisoned, though not fatally, but one son, as we have already seen was permanently disabled due to effects of Thallium on his Central Nervous System. Interestingly, Trepal was so confident of his "perfect murder" that when the investigating officials came to him for enquiries, instead of keeping quiet, or expressing his ignorance in this matter, he speculated that someone might poison people to get them to move out of the neighborhood! This immediately allerted the officials, who at once started thinking in terms of poisoning. When Trepal's home was searched, a small vial of thallium nitrate - generally unavailable to the public - was found there. Other incriminating things found in his house were a detailed homemade notebook titled, "General Poisoning Guides," with several entries on thallium, and an extensive store of dangerous chemicals. He was found guilty by the court, and sentenced to die."

"Amazing! It appears we have another Trepal on our hands now. It is now sure that poor Ramlal died due to Thallium poisoning?"

"Yes, and I confirmed this by several other means too. First of all I analyzed for thallium in his urine, and it was present in high quantities. Furthermore there was a widespread destruction of nerve cells in the brain. Liver and kidneys were damaged as is usually seen in thallium poisoning."

"So from an apparent natural death, you have suddenly discovered murder in it. Who could possibly have poisoned him?"

"Tarun, before you came, I had already given my findings to police and the police has done a detailed investigation subsequent to my report. You are right that someone was indeed trying to poison him. on detailed investigations, it was found that a colleague Karim was mixing Thallous acetate in his tea daily for some days. He had an old axe to grind with Ramlal. Faced with the scientific evidence, the police questioned Karim and he admitted his guilt. Thus a poisoner who could have gone scot free was caught with the help of forensic science."

"Oh, how very clever of you doctor. This was a most interesting discussion. Tell me what are you going to tell me the next time?"

"Tarun, next time, I would tell you about a very deadly poison - Capsaicin. "