Stain-spotting a snap
A CAMERA that can detect and date blood traces is set to revolutionise crime scene investigations.
A new hyperspectral imaging device that can scan for the visible spectrum of haemoglobin could speed up police inquires, lead to more convictions and reduce the number of miscarriages of justice, its creators have claimed.
A prototype built by researchers at Teesside University has demonstrated extraordinary levels of laboratory accuracy.
Month-old blood samples can be dated to within a day, while fresh traces have been pinpointed to within an hour of their being taken, potentially helping police to establish a time of death immediately – a process which at present can take several days – and allowing detectives to build a more rapid chronology of events.
Blood samples and splatter patterns are one of the most commonly used forms of prosecution evidence in cases of violent crime.
It’s believed the technology could also be applied to other fluids including sweat, saliva and semen, which could improve conviction rates for rape and other sexual assault.
Dr Meez Islam, a physical chemist and reader in the university’s school of science and engineering, who led the team working on the project, said identifying bloodstains often posed serious problems. Forensic teams were still working with techniques devised a century ago, and there was currently no effective way of dating blood.
“Often you go to crime scenes and what appears to be blood isn’t blood. Blood on dark backgrounds can be hard to see and there are traces of blood that are not visible to the naked eye. What this does is provide at-the-scene identification of blood and speeds up the investigative process, as items do not need to go back to a laboratory to be examined. To use hyperspectral imaging in a way that scans the crime scene for blood also vastly reduces the chances of missing a bloodstain,” he said.
The new technology, to be unveiled at a forensic science conference in Manchester next month, uses a liquid-crystal tunable filter and is able to offer immediate results. The filter works by isolating different wavelength bands of colour, so it can detect blood against other similarlooking substances or in hard-to spot locations such as on red clothing, carpets or furniture.
Because blood changes colour over time, from bright red to muddy brown, at a known rate, the device is able to put an accurate age to a sample. At present, forensic scientists must paint chemicals on to areas where they believe blood may be present, hoping to produce a reaction with iron found in haemoglobin. It is a procedure demonstrated in TV dramas such as CSI.
But failure to locate samples has plagued a number of high-profile cases. In the investigation into the murder in 1993 of the teenager Stephen Lawrence, detectives were hamstrung by their inability to find any physical evidence linking the suspects to the killing.
It was only during exhaustive laboratory retesting during a cold case review that a spot of Stephen’s blood was found on the seam of the collar of a jacket belonging to his killer, Gary Dobson. In the case of the south London schoolboy Damilola Taylor, murdered in 2000, experts missed a bloodstain on a tackie belonging to one of his killers.
Islam said he needs £100 000 (R1.6 million) to create a working model. “This is a fairly small investment for a relatively large societal impact,” he said. – The Independent on Sunday
A BETTER PICTURE: New blood camera will help forensic experts.