Root causes

PUBLISHED : Sunday, 08 March, 2009, 12:00am
UPDATED : Sunday, 08 March, 2009, 12:00am

Professor Paul But, a biologist at the Chinese University of Hong Kong with a PhD in botany, has an unlikely nickname among his peers. 'They call me the Ghost Buster.'

But's research includes the study of indigenous plants and vegetation in the region. The bulk of his work is concerned with the authentication and quality control of traditional Chinese medicine (TCM). He has identified herbs and foods that have poisoned people and even caused death. But earned his nickname while working on a case in which he identified a poisonous herb that killed two people who had drunk it as an infusion.

'It was supposed to be clematis root which is used in TCM but there is a herb that looks very similar which is called 'poisonous Podophyllum root'. In Cantonese, we call it gwai kau which means 'ghost mortar'.'

The professor and his team developed an 'instant method' to help identify the herb, so the mistake wouldn't be repeated.

Forensic botany, like other forensic disciplines, is based on the principle that a criminal always leaves something at the crime scene, or takes something away, although in Hong Kong it has limited applications, despite the fact that a high proportion of the territory consists of green areas.

David Clarke is a former Hong Kong government chemist and has assisted in high-profile investigations such as the infamous 'jars' murders of the 1980s in which a taxi driver dismembered the bodies of a number of women and hid them in containers in his bedroom.

'There's not much call for [forensic biology] in Hong Kong,' he says. 'Most of the murders take place in the city; in apartments, offices and on the street. There's not much pollen there and any plants you might find are probably in pots, not indigenous.

'Lugging a body around off the beaten track, especially given the hilly terrain, probably at night, doesn't seem to appeal to the average Hong Kong murderer, thank heavens.'

But's department, on occasion, is contacted by the hospital authority, the consumer council, the coroner's court and the customs and excise department, to analyse evidence in criminal cases. He says that from the samples his department is sent, data and interpretation can be provided which, in some cases, leads to further action.

The professor is also called upon to give evidence in court. This could include the identification of a certain plant species and locations where they grow. 'We would be able to identify a species of plant and its source by looking at the spores of the pollen and the size of the pollen grain and its DNA,' says But. 'We may narrow it down to an area with a large degree of reliability ... because we know the different vegetation types that cluster there.'

But says he is aware of the use of forensic botany in Britain and says, if called upon, he could use his scientific expertise in assisting a criminal investigation here.

'The main value in such an expert's work is normally in helping the police to move in the right direction,' says Clarke. 'The results don't always necessarily link a person to a place, rather they help with the chain of events and clearly sometimes to find bodies.'