The vital piece of evidence which helped convict two of Stephen Lawrence’s killers was discovered due to the tenacity of the experts who were “clever” and “imaginative enough to find it”, a forensic scientist on the case has said.

Professor Angela Gallop returned to the Stephen Lawrence investigation in 2006 after having first reviewed the forensic evidence in the race-hate case in 1995.

She told BBC Radio 4’s Desert Island Discs the key information was found during her team’s second investigation because they looked at the evidence “from a different angle” to see if anything had been missed during the original investigation.

She told the programme: “It is so true that every contact leaves you have just got to be clever enough and careful enough to find it and imaginative enough to find it.”

Five men had been arrested over the racist murder of 18-year-old Mr Lawrence, who was stabbed to death in an unprovoked attack Eltham, south-east London, on April 22 1993.

It took until 2012 before two men, David Norris and Gary Dobson, were given life sentences after being found guilty of murder.

Prof Gallop recalled that good scientists had looked for blood on the suspects’ clothing but had not found it.

Taking a different approach saw them examine the packaging in which some of the suspects’ clothing had been stored since the killing and, thanks to the advances in forensic technology, they discovered a microscopic flake of blood in the textile fibres of one of the suspects’ jackets.

The blood matched Mr Lawrence’s DNA.

The scientists then examined the jacket for an original blood stain.

Prof Gallop recalled that inside the packaging, scientists had found a “tiny flake of blood with two fibres encased in it, so obviously there at the time the blood was wet”.

She added: “Then we thought if we have found it in the packaging, it must be the remains of an original blood stain somewhere on the garment and we kept missing it.

“That’s when we got out a microscope and went over the whole thing in detail.”

This detailed search was “very difficult” and “exhausting” because the white and black fibres on the garment meant that overall it looked grey.

She added: “Eventually inside the back of the neck, which is sort of where you might expect to find a tiny spot of blood from an attack like that, we found the remains of a spot of blood.

“We tested it and it contained Stephen’s DNA and so eventually we got there.”

Prof Gallop has attended two memorial services for Mr Lawrence and it has left her with the feeling that “things are not, or certainly weren’t, fair”.

She was also struck by the eloquent tribute made by Mr Lawrence’s bother Stuart, as he talked about him as “this young lad who had so much to look forward to and was clearly such a nice boy, that was just heartbreaking really.”

Mr Lawrence’s killing led to the landmark Macpherson report, published in February 1999, set out wide-ranging proposals for reform after it found that the Metropolitan Police investigation into the murder had failed in part due to “institutional racism”.

Prof Gallop told the programme: “This case wasn’t investigated as thoroughly as I would like to think it would be today.

“I think the McPherson Inquiry went into that in great detail and talked in particular about how police culture had to change and I think I felt very strongly about that.”

Over the course of her 50-year career, the Oxford-born scientist has been known for going the extra mile with determination and passion to get the evidence she needs.

This included reconstructing scaffolding in her back garden and getting her husband, who is also a forensic scientist, to help with the scene as she looked in to the killing of Roberto Calvi.

He was dubbed “God’s banker” because of his work with the Vatican, and was found beneath London’s Blackfriars in 1982.

His death was originally ruled a suicide but later judged to be murder.

The work of Prof Gallop’s team also helped to exonerate the men who were accused of the murder of Lynette White, 20, at her docklands flat in Cardiff in February 1988.

In 1990 five men who became known as the Cardiff Five, all of whom were black or mixed race, were tried for the murder and three of them were sentenced to life in prison.

The work of Prof Gallop’s team also helped to prove, 11 years after the attack, that Jeffrey Gafoor was the real murderer.

He was a recluse who was eventually tracked down through a familial DNA link after the scientists, who looked at anything that had not previously been tested at the crime scene, found a bloodstained “tiny piece of cellophane of the end of a cigarette packet”.

Blood was then found on the skirting board and the front door after the scientists asked police to remove them.

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