Scientists probe secrets of blood stains

TV shows such as CSI have brought the study of blood stains to the fore.

The study of blood-splatter patterns, made famous by popular TV crime shows CSI and Dexter, is being looked at by New Zealand researchers.

University of Canterbury and Institute of Environmental Science and Research (ESR) staff are teaming up to study how blood forms stain patterns. Their work will help police, forensic scientists and courts interpret evidence.

Bloodstain pattern evidence is often crucial in police investigations and trials, but can be difficult to interpret.

"The forensic science community has put a lot of effort into working out rules for interpreting bloodstains," said University of Canterbury mechanical engineering senior lecturer Dr Mark Jermy.

"We are attempting to make clear the science behind these rules," he said.

Bloodstains can provide key information on the position of the victim and assailant, the type of weapon and the number of blows.

It can be particularly useful when trying to determine whether a death is suicide or murder.

"Several murder cases have been retried due in large part to confusion over bloodstain evidence," Dr Jermy said.

"This confusion arises from a lack of fundamental understanding of the complex physical processes which generate bloodstains.

"We plan to develop a deep understanding of these processes by studying wounding by gunshot and blunt impact using realistic physical models of body parts under controlled laboratory conditions.

"Our group is one of the very few research groups performing this work in the world."

The work is led by ESR, which provides scientific analysis services to the police.

New Zealand has 86 homicides a year on average, with 93 per cent of cases ending in arrests the same year. There are approximately 35,000 acts intended to harm every year, of which 84 per cent end in arrests.

But just 44 per cent of homicide prosecutions and 58 per cent of cases involving acts intended to cause injury result in convictions.

Dr Jermy said there were opportunities for better detection and better use of evidence in court to resolve more violent crimes and achieve just outcomes for suspects, victims and their families.

"One of our research areas is to understand the mechanical properties of the human brain under high impact cranial gunshots."

One postgraduate student is using high-speed video to record bullet impacts on synthetic materials developed to mimic the human brain.

The researchers hope it will lead to an understanding of where the material ejected from an impact will land and what kind of stain pattern will result.

"Another project is looking at a computer code that can predict blood droplet trajectory," said Dr Jermy.

"This will help investigators to ascertain where an impact event occurred in the crime scene."