Patricia Wiltshire speaks with some regret as she recalls her involvement in the investigation into the murder of two soldiers outside a barracks in Co Antrim.
And there is sadness remembering another case she was involved in, the terrible death of baby Carrie, a newborn stabbed and discovered in a black plastic bag in Carryduff more than 20 years ago.
Massereene
A forensic scientist who has worked on hundreds of major criminal investigations, Ms Wiltshire flew in following the murders of Mark Quinsey (23) and Patrick Azimkar (21) the only British Army soldiers killed in the north since 1998.
The pair, due to be deployed to Afghanistan, were shot dead outside Massereene barracks in Antrim in 2009, believed by dissident republicans.
Investigators had seized shoes and a holdall bag believed to be connected to one suspect, along with discovering a burnt out Vauxhall linked to the attack.
Prof Wiltshire, who had played a key role in identifying Ian Huntley, the murderer of Holly Wells and Jessica Chapman, was brought in to examine soil and other samples from the scene and compare them to the items seized and discovered.
She studied the pollen and spore trapped in soil, leaves and plants to try and match a suspect to a crime scene and the believed getaway vehicle. The study of the microscopic grains to help establish a time line.
Material was taken from the wheel arch, the accelerator, brake, clutch and mat of the car.
“This person had stepped in a wet ditch where there was sphagnum moss and where there were loads of ferns. The person had walked through wetland,” she told investigators.
She was intrigued, after studying material inside the holdall, to discover the fungal spore could only have originated in very hot soil, over 35 degrees.
“It was too hot for a greenhouse. It was believed the material came from Libya, that the guns in the holdall came from Libya,” Prof Wiltshire remembers.
Ian Huntley admitted the murder of Holly Wells and Jessica Chapman in Soham
Unlike being part of teams successful in helping convict killers, including Huntley and the murderer of 13-year-old Milly Dowler in 2002, Levi Bellfield, the scientist did not give evidence in the Massereene case because she required surgery.
A judge ruled the evidence could not be admitted without Prof Wiltshire being able to be cross examined by the defence. The defence did have a number of expert witnesses ready to contradict Prof Wiltshire’s evidence.
One man was acquitted of the murders, while a second had a conviction later overturned.
Prof Wiltshire (82) and originally from Wales, has helped police in more than 300 criminal investigations over the last three decades.
Her new book, The Natural History of Crime, focussing on a number of high profile cases, has just been published
She explains it is in no way strange to conclude at least one of the guns in the holdall might have come from Libya despite arms shipments from the north African country ending in the late 1980s.
“Pollen and fungal spore can stay forever if in dry or acidic,” the scientist says, adding she was involved in a cold case that ended with the conviction in the murder of a boy in 1983.
She notes: “Pollen can survive in rocks for millions of years.”
Forensic ecology is based on piecing together a profile of a place based on the traces of pollen and spore, then matching that to what is found on other material.
It is not an exact science, not least, as an example, suspects may have walked through many types of soil or vegetation.
The forensic ecologist can identify many similarities between a scene and material linked to a suspect. In some cases, they work with rare pollen, including from flowers that widespread, with Ms Wiltshire citing clover as an example.
“There is a little bunch of tiny, tiny flowers with very little pollen released. It is very rare.”
Prof Wiltshire says the science can be used in an investigation to help secure a conviction, propel a suspect to change a plea as in the Soham case, for intelligence purposes, corroboration and, importantly, elimination, allowing investigators to deploy resources elsewhere.
The scientist, also a botanist, was largely working on the reconstruction of ancient environments when first called by criminal investigators in 1992. Police had approached The Royal Botanic Gardens, Kew, and they were directed to Prof Wiltshire.
“It was not major leap to modern environments. It became a whole part of my life eventually,” she adds.
Over the following years, she was called in by police forces across Britain as well as the Garda and the RUC, later the PSNI. In one murder case Ms Wiltshire was involved in she managed to identify many similarities with clothing linked to an IRA operator involved in a fatal ambush to the wall he had leaned up against.
Baby Carrie
Then in March 2002, she received a call from police following the discovery of a new born baby in a bin bag at the Duck Walk behind Lough Moss Leisure Centre in Carryduff.
The baby girl was stabbed multiple times but was found to have died from strikes to her head which fractured her skull. The umbilical cord was still attached.
Police believed she was buried in a garden then some weeks later the body was removed, placed in the bag and brought to the Duck Walk.
Prof Wiltshire took samples from inside the bag, from the body and around the scene.
She examined peat recovered from inside the bag but concluded it could not have come from anywhere in Ireland or Britain.
After contacting different garden centres, and examining the peat sold as Irish, she discovered it was largely made up of material from Estonia. The information may have helped narrow down the number of gardens where the baby was originally buried.
The police investigation into the death was intensive, including DNA samples taken from some 1300 women. But the mother has never been identified and the baby’s grave is marked: “Baby Carrie - Known Only Unto God.”
“That was very sad and there was also a woman in a very vulnerable position,” says Prof Wiltshire.
The forensic ecologist, who many times has been at scenes where victims are still close by, admits she is affected but “you have to detach yourself”.
“You do have regard for the victims and always feel sorry for the families.”