The science behind crime scenes

Walking into a blood-spattered room would be enough to give most people nightmares, but for crime scene investigator Dion Sheppard it's just a series of scientific problems.

If there is a stray hair, fingernail or print that doesn't belong, the young forensic scientist will find it, bag the evidence, and figure out how it fits in the bigger picture.

Sheppard has been at the Institute of Environmental Science and Research (ESR) for just five years but has already been to his fair share of crime scenes.

The most recent was Antonie Dixon's samurai sword attack on Simonne Butler and Renee Gunbie.

"That was a really interesting scene," the 29-year-old says. "One of the main parts of work at the scene is interpretation of blood splatter patterns and trying to figure out what has gone on.

"There was a lot of blood and very interesting patterns. If you sever an artery you get spurts of blood that travel long distances. If you have blood on a weapon and the weapon is moved you get cast-off, which is where blood is flung off a weapon."

What the ESR team find helps police in their reconstruction of events.

"It's a case of putting little things together to build up the big picture, but that's what I enjoy - I love the problem solving," says Sheppard. "On the scene or back in the lab, when you find something and things start coming together it is a great feeling."

Like most investigators, Sheppard is not bothered too much by dead bodies.

The ESR team is more concerned about getting the job done quickly and thoroughly so fresh evidence is not compromised.

"It's usually after the work and you reflect on what you have seen that some cases have more of a lingering effect," he says. "Cases with children who have been beaten to death are difficult."

ESR provides counsellors for staff, and after big cases investigators talk about the case and how they are coping.

Like their CSI: Crime Scene Investigation counterparts, ESR investigators are often married to their jobs. They are on call one week in every five.

While Sheppard insists his job is not always like the popular TV series, he admits that high profile cases - like William Bell's murder spree at the Mt Wellington RSA in 2001 and the conviction of Palmerston North man Mark Lundy in 2000 for the murder of his wife and daughter - are particularly intense.

"There is a lot of pressure in some cases. There is pressure from media attention; pressure from yourself to get through the items; pressure from the client to get it done."

Crime scenes vary - some are dirty, some bloody. Sometimes investigators are forced to work closely alongside decomposing bodies in small, cramped spaces.

"It doesn't take long for a body to start to get pretty unpleasant," Sheppard says. "A day or two in a car in summer and it's pretty bad."

Investigator Sally-Ann Harbison has been attending crime scenes since 1988 and has seen a few staff members quit because they can't handle the work. She has been to hundreds of homicides - up to 20 a year.

The only ones that bother her are the ones that reflect her own life - such as the ones that remind her of her grandmother or her daughter.

"Otherwise it's more of an intellectual exercise. There are so many things you have to think about and do, that you just get on with it.

"You have so many checklists and problems to solve you don't have time to focus on the dead body."

In the lab, DNA investigators like Sarah Cockerton take evidence collected by the scene investigators and run matches - either incriminating people or clearing them from police investigations.

The 28-year-old was involved in the Teresa Cormack case, and was thrilled when a match came through.

"I was doing the mass screen of a lot of individuals and collating all the results and passing information on. It is a nice feeling when you get something finished and you know you have helped in the investigation."

Cockerton also has to present the evidence at court - explaining to juries how DNA is often the missing piece of the puzzle. "When you look at the jury and you can see they actually understand what you are saying and they can make a good decision because of it - that's a great feeling."

- Herald on Sunday