Stephen Lawrence murder: How case hinged on bloodstain that was just ¼mm wide

A team of scientists at a private company, LGC, was asked to “start from scratch” in working to uncover evidence against whoever killed Mr Lawrence.

It 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. Bloodstains 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, in about 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 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 bloodstain 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 Metropolitan 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 through to 1996 the methods used were not being targeted at microscopic bloodstains – certainly the size of the stain found later on the [suspect’s] 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 bloodstains 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 a huge amount about how you look for evidence, and where 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 microscope, and 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 Dob-son’s collar was not caused during saliva testing, as the defence claimed.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.”

During the trial, the jury was also shown police surveillance footage from 1994 of Dobson and David Norris using racial slurs. In the film Norris also launched into a violent tirade about how he would kill and torture black people.

As they were led away, Dob-son told the jury: “You have condemned an innocent man here. I hope you can live with yourselves.”

His mother Pauline called out: “He didn’t kill that man.”