Some criminals survive on cunning, some are plain stupid, some are plain angry, and others survive on sheer audacity. This is a case of the latter.

The information presented here is but a small part of the total evidence presented in the eventual trial. Following the usual convention, when the term pollen is used it also includes spores from ferns and fern allies.

It was dark but only late afternoon in the middle of winter in northern New Zealand and the victim, who we will call Mary, was in bed asleep with the back door unlocked. She was waiting for her live-in boyfriend to return home. Two suspects entered the house intent on robbery. They stole a wallet and purse which were sitting on the kitchen table. One suspect entered the bedroom and saw Mary asleep and got onto the bed with her and started fondling her breasts while his associate watched from the foot of the bed. Mary awoke and naturally screamed. The two assailants ran off into the night, but not before Mary had grabbed the more audacious suspect and wrestled off his denim jacket, which was eventually left behind on the kitchen floor.

In the meantime Mary's boy friend, who we will call George, returned home to find his partner on the telephone to the Police. At the same time the suspect who had got into bed with Mary and who had apparently been watching the house, returned, knocked on the door and asked George for his jacket back, which he could see from the door. George, not having spoken to Mary yet was a bit confused over what had happened and did not respond immediately. The suspect then pushed passed him, grabbed the jacket and again rushed off into the night the jacket flapping loose in his hands.

Neither suspect made any attempt to disguise himself and the prime offender, who got onto the bed beside Mary, was soon located by a Police dog in a nearby street and arrested. He was interviewed but denied any knowledge of the incident and did not identify anyone who could have been with him. Mary and George both identified him as the man who was sitting on the bed with her when she awoke and the man who had claimed his jacket back. His associate was never identified and the stolen wallet was not found, but the purse was located near the crime scene the following day. Also a small amount of money was never recovered.

The suspect was young and identified as a student. He was well known to the local constabulary.

A local scene examination confirmed that the two burglars had entered an unlocked door leading directly into the kitchen. The offender was charged with indecent assault on a female and burglary with a potential maximum penalty of seven years imprisonment if found guilty.

The Hypericum bush outside the kitchen door

Immediately outside the kitchen door and partly covering the entrance and path to the street was a small bush in full flower. The flowers were pentamerous, yellow with long stamens and a long style and the Police were certain that the offender in going through the door and down the path would have brushed against this bush each time he passed. The Police confirmed that bright yellow pollen readily came off this bush as they examined it. Four months later a control sample, originally collected two days after the crime was committed, was sent to the Palynology Laboratory of the Institute of Geological and Nuclear Sciences, where the plant was identified as a Hypericum.

Fertile anthers from the control sample, a flower from the Hypericum bush, was processed separately and in isolation from the evidential samples that were processed later.

Hypericum pollen turns up every now and then in forensic samples, but in my experience of over 1000 forensic samples, never more than a trace or maybe 1%. When someone brushes against flowering plants that release pollen easily, the pollen often occurs in clumps as well as in unusually large numbers. With such large numbers and with the pollen both loosely attached and pressed into the clothing some transfer of pollen from the prime source, that is the part of the clothes that came into direct contact with the flowers, to clothing that could not or did not come into contact with the flowers is possible.

The day following the offence the offender's clothing was taken from him for forensic examination including pollen analysis. These consisted of a blue denim jacket, a black polo shirt, black nylon track pants, a dark blue baseball cap, separate black track shoes, and brown chequered socks.

Pollen in clothing tends to reflect the history of each individual item, and as such it is not expected that each item would produce the same pollen assemblage. Of course, in the unlikely event that all separate items of clothing had always been worn at the same time, then the pollen would reflect this. The pollen recovered from the shoes were very similar in both cases, as could be expected. Because the socks had been packaged together they were processed as one item, so we could not tell if there was any significant difference between them. In this case the only history that was important was the presence or absence of Hypericum pollen. Therefore only the Hypericum pollen was counted in relation to all other pollen types.

Abundant and diverse pollen was recovered from all items of clothing. All pollen was removed from the baseball cap, shoes and socks. Only those parts of the denim jacket, track pants and polo shirt thought likely to have come into contact with the flowering Hypericum was examined first and this amounted to the processing of about two-thirds of each item. As it turned out this was all that was needed.

Detail of the Hypericum flower

The track pants contained 14% Hypericum pollen, the denim jacket 24%, and 27.5% on the polo shirt. All these items must have been in direct contact with a flowering Hypericum bush shortly before they had been seized by the Police. The socks and shoes had traces of Hypericum pollen. These items may not have been in direct contact but may have kicked up pollen from the path beside the bush or pollen could have transferred from the other clothing onto the socks and shoes. The baseball cap, which was unlikely to have come into direct contact with Hypericum did not contain any Hypericum pollen.

Also the amount of pollen still with cell contents intact indicated that the contact with the plants was relatively recent. But without research to determine just how long an interval of time it would need to desiccate this pollen type under different environmental scenarios, a time frame to the crime could not be established using the pollen. However, the garments were studied at least 5 months after the event and many of the grains still had cell contents preserved. The number of pollen grains in clumps, even after processing, indicated that the pollen could not have been aerially dispersed but must have arrived on the clothing in bulk directly from flowers.

The pollen from the control sample was identical in size range, shape, development and colour to the pollen from the jacket and other clothing.

Examination of the scene near where the main offender lived, and the areas he was known to have frequented in the few days before the crime failed to locate any other Hypericum plant that he could have come into intimate contact with. It is, of course, possible that the offender had been in contact with another bush immediately before committing the crime or immediately before he was apprehended. But then what are the chances of picking someone at random and finding on their clothing such a large amount of Hypericum pollen. With my experience of looking at about 30 cases per year for a number of years that percentage of Hypericum pollen had never been even remotely approached.

This pollen evidence, of course, is circumstantial and would on its own not convict anybody of an offence. But with the other evidence at hand, including the identification of the offender by the victims, it provided enough direct and circumstantial evidence for the courts to declare that the offender was indeed guilty of burglary and indecent assault on a female and sentenced him appropriately.

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  This article first appeared in CAP Newsletter 26(1), 2003.