Hypericum pollen determines the presence of burglars at the scene of a crime: an example of forensic palynology

Abstract

Two male intruders entered a house in which the sole female occupant slept having left the back door unlocked for the return of her live-in boyfriend. She awoke and saw strangers in her bedroom. The intruders ran off, one leaving a jacket behind on the kitchen floor. One of the intruders subsequently returned to recover his jacket, but in his rush to leave the house he brushed against a flowering Hypericum bush growing just outside the back door. A suspect was arrested later that day and charged with indecent assault on a female and burglary, but denied any involvement and refused to name any associate. A day following the offence the suspect's clothes were taken for forensic examination. Pollen analysis of selected parts of his clothing showed that his track pants contained 14% Hypericum pollen, denim jacket 24%, and polo shirt 27.5%. Traces of Hypericum pollen occurred on other items. Most of these pollen grains still had their cell contents preserved and were on the clothing in clumps consistent with having recently been collected by the clothing and not having been aerially dispersed. The pollen from the Hypericum bush was identical in colour, shape, development, and size range to the pollen from the clothing. The clothes had so much Hypericum pollen on them that they had to have been in direct and intimate contact with a flowering bush. Pollen evidence is by its nature circumstantial and often cannot be used on its own to convict, or more strictly to determine the truth. The suspect may have been in contact with Hypericum elsewhere, but detailed investigations indicated that this was unlikely. In 30 years of New Zealand forensic work Hypericum had only ever been found on clothing in trace amounts. This is but one way in which forensic palynology can assist law enforcement agencies to determine the history behind a criminal action, and demonstrates that forensic palynology should be considered as an integral part of any criminal investigation.