Tiny forensic details prove key in Stephen Lawrence case
Tuesday 03 January 2012
Success in cold cases including the death of Damilola Taylor sparked a new review which uncovered key forensic evidence in the Stephen Lawrence investigation.
A team of scientists at a private company called LGC were asked to "start again from scratch" in working to uncover evidence against whoever killed Mr Lawrence.
They carried out months of painstaking research before DS Alan Taylor and forensic scientist Rosalyn Hammond undertook the mammoth task of making sure forensic evidence had not arisen through contamination.
The team at LGC took a much wider approach than had been adopted before.
When examinations were carried out in 1993, it was believed that any textile fibres would have fallen off the suspects' clothes in the two weeks between the killing and their first arrest.
Blood stains or hairs also had to be of a certain minimum size for DNA profiling to be carried out.
But after successful convictions in a number of cold cases, around 2006 detectives realised that starting from the beginning could yield results.
Gary Pugh, Director of Forensic Services for the Metropolitan Police, said: "The Damilola Taylor case...involved what LGC have done in going right back to basics and starting from scratch. Many of these cases have had reviews over time but quite often they're with a presumption that if nothing's been found the items aren't re-examined.
"What I think we've done here and in previous cases is start again from scratch and that was the brief we gave LGC in this particular case."
The Damilola Taylor case involved the key discovery of a blood stain on the shoe of one of the defendants.
Under double jeopardy legislation, investigators were required to prove that scientists had done all they could previously to find the Stephen Lawrence evidence, and that there was no lack of due diligence.
Alan Tribe, manager of the Met Police evidence recovery unit, explained that scientific methods advanced significantly between the 1990s and 2007 when the cold case review started.
He said: "In 1993 though to 1996 the methods used were not being targeted at tiny, microscopic bloodstains - certainly the size of the stain found later on the jacket. This is principally because such stains would not have been capable of being subject to DNA profiling during the time."
It was only from 2000 that blood stains invisible to the naked eye were able to be analysed for DNA, and then the techniques were in their infancy.
Dr Angela Gallop, who worked for LGC during the cold case, said: "The emergence of the findings in this case depends partly on improving methodology, this is lessons learned from other cases in how to find these truly tiny amounts of evidence, alongside developments in technology which allowed us to actually analyse them."
She went on: "We've learned such a huge amount about how you look for evidence and where you look for it and when you look for it, combined with the fact that we now have much more powerful technology to analyse it."
The team used cutting-edge techniques such as examining suspect items all over with a low-powered microscope, and they sent a 2mm fragment of hair to the US to be tested for mitochondrial DNA.
Body fluid specialist Edward Jarman and his team developed their own experiments to show that the bloodstain on Gary Dobson's collar was not caused during saliva testing, as the defence claimed.
He said: "We undertook a number of experiments looking at blood from both the packaging of the jacket and also from a number of Stephen Lawrence's items to see if they could solubilise or if they could be affected by getting wet and that resulted in the stain on the collar, and we weren't able to replicate the stain on the collar under all those tests."
The stain measured just 0.5mm by 0.25mm.
Mr Jarman added: "I think in isolation it's probably the first time such a tiny stain has had such a bearing potentially on a case."
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