The original chief forensic scientist in the Stephen Lawrence case was forced to admit last night that crucial evidence in the case may have been contaminated as long as 12 years ago.
Adrian Wain, the scientist in charge of the investigation into the killing of the black teenager for 13 years, was brought in by the prosecution to give evidence in the murder trial of Gary Dobson and David Norris.
But in a twist, the Old Bailey jury heard that Mr Wain had cast doubt on whether key exhibits had been contaminated – long before a later forensic examination discovered new evidence on which this trial hinges.
Mr Lawrence, 18, was on his way home on 22 April 1993 when he was set upon by a group of racist men and stabbed twice in what was to become one of the most notorious murders in recent British history.
Eighteen years on, the murder trial revolves around blood spots and flecks as well as fibres and hairs found on the suspects' clothing. The prosecution insists that the evidence, found when scientists re-examined the garments during a cold case review in 2006, proves the pair were among the violent gang.
The defence, however, has rejected it as merely a "teaspoon" of evidence, the product of cross contamination over the years. Mr Dobson, 36, and Mr Norris, 35 both deny murder.
Yesterday Mr Wain insisted that his staff in 1993 had done everything to protect the evidence while it was in their laboratory. But in cross-examination Timothy Roberts QC, for Mr Dobson, produced a damning report from a senior officer made in 1999.
Detective Chief Superintendent Barry Webb wrote that both Mr Wain and the exhibits officer had questioned "the deterioration of the packaging of the clothing exhibits in this case".
"Original tape seals used when the items were seized in 1993 had become so ineffective that, in Adrian Wain's view, in the event of alien blood cells being found on the suspects' clothing in any subsequent examination, he would be unable to rule out the possibility of contamination," he wrote.
Mr Roberts produced a letter by the scientist two years later, responding to requests from police officers to test Mr Lawrence's jumper and body-warmer for fibres. In it, he wrote that he was "reluctant" to do so, given that he had only found one fibre with a weak match to Mr Dobson's jacket on Mr Lawrence's jacket and "my concern about the possibility of contamination in this case".
"I think I was aware that the items had been in and out of the laboratory. I didn't have control of them outside the laboratory and we didn't know whether they had been in the same locations. We knew the packaging was deteriorating and, yes, I had concerns about contamination," Mr Wain told the court yesterday.
Earlier, the trial was told that repeated examinations had found no definitive trace of blood and only a few fibres that were considered very weak evidence. Central to the prosecution's case is that a minute spot of Mr Lawrence's blood was found soaked into the collar of Mr Dobson's jacket. The trial continues.