16 June 1998

University of Queensland botanists have used the latest high tech methods to help Queensland police identify source crops of distributed cannabis materials and prosecute drug offenders.

Spores and pollen caught on clothes, packaging materials or cars can also be used as a kind of 'environmental fingerprint' helping police to place criminal suspects at scenes of crime.

In the past 18 months, University Botany Department researchers have helped Queensland and Northern Territory police in several drug-related cases and one homicide by providing evidence based on stable carbon and nitrogen isotope proportions in plant samples and associated pollen.

Led by Professor George Stewart and Senior Research Fellow Dr Mary Dettmann in conjunction with Inspector Paul Stewart of the Queensland Police Service, the research project began in 1996 funded by a three-year, $127,000 National Drug Strategy Law Enforcement Committee grant.

Dr Dettmann said the recent cases highlighted the admissibility of botanical evidence in the State's court rooms.

Authorities could use forensic evidence provided by the plant world to investigate a wide range of illegal activity ranging from serious crimes such as murder through to food fraud, she said.

Following Professor Stewart's relocation to Western Australia, Department researcher Dr Susanne Schmidt and PhD student Trish Court are working on the plant isotope aspect of the research involving the characterisation of stable isotopes - different forms - of basic elements such as nitrogen and carbon in plant matter and in soils.

The proportions of these stable isotopes vary according to the environmental circumstances under which the plant has grown - for example, in fertile or poor soils and under a warm or cold climate.

Ms Court is investigating isotope signals of cannabis grown under controlled conditions of temperature, water and nutrient levels. The isotope signals are analysed using mass spectrometry.

Dr Dettmann said the spores and pollen in the soil around plants were easily picked up by shoes and car tyres.

If a crime was later committed, a person could be placed at the scene of the crime or eliminated from police inquiries by checking the nature of the minute plant fragments on their clothing or cars, she said.

'The soil stuck to human shoes or to car tyres can be examined for these isotopes as a further guide to the geographical region the material has come from. This provides corroborative evidence to back up initial discoveries from the pollen and spores,' she said.

'Geographical locations can be pinpointed more accurately using both these systems.'

According to Dr Dettmann, information correlating plant spores and pollens with the areas in which they occurred would eventually be stored in a special plant databank. Police could then access the databank for information once plant fragments were found in connection with a crime.

'The police hope that the pollen and spores found on the suspect or their car could be used to place the person at the particular geographical region and plant community where a particular offence has taken place,' Dr Dettmann said.

'This forensic botanical evidence could also be used by police to substantiate alibis. If someone says they have been at a place, police can check their clothing and car for signs of the plant spores and pollen which are sourced from plants that occur in that region.'

Although largely overlooked in Australia until recently, in other countries such as New Zealand, police have commonly referred to botanical evidence to help unravel crimes,' she said.

She said the techniques could also be used as a form of quality control for some foods.

'For example, honey could be screened to determine whether it was pure - that is, derived from the pollens of one as stated on the label - and not adulterated by other ingredients such as cane sugar,' she said.

For more information, contact Dr Dettmann (telephone 07 3365 2744) .