A tiny bloodstain found on the jacket of a man accused of murdering Stephen Lawrence could have come from the knife pulled from the teenager's body during the fatal attack by a racist gang, the Old Bailey heard yesterday.
The stain on the jacket's collar, discovered 15 years after the killing, most likely happened within minutes of the attack while the blood was still wet, said the forensic scientist Edward Jarman.
The jacket was found by police in a wardrobe at the home of Gary Dobson, 36, some two weeks after the murder. Mr Dobson and his co-defendant, David Norris, 35, both deny killing Mr Lawrence, 18, in Eltham, south-east London, in 1993. The court has heard he was "swallowed up" by a gang of about five white youths as he waited for a bus.
Previous analysis of the jacket failed to show any of Mr Lawrence's blood until a cold case review team painstakingly scoured the jacket for signs in 2008, the court was told. The bloodstain – measuring just 0.5mm by 0.25mm – was found soaked into the collar. The prosecution told the jury there was a one-in-a-billion chance that the blood did not come from Stephen Lawrence.
Mr Jarman told the court that the amount of blood at the murder scene was likely to be small and could have got on to the jacket after spots flew through the air during the attack. Mr Lawrence was wearing several layers of clothing and the attack was over in seconds, according to witnesses.
"There was a potential that the blood could be transferred by the weapon itself when removed from the victim or [be] the actual blood from the injury itself," Mr Jarman told the court. He said the blood was likely to have been in contact with the coat "a very short time after the incident" and said such a small stain would have taken only a couple of minutes to dry.
The defence has claimed that evidence of the teenager's blood on the jacket is a result of contamination after poor handling and storage.
Mr Jarman said yesterday that if someone had not been wearing the jacket at the scene, the blood would have had to have been transferred shortly afterwards. He told the court that a thin layer of blood on someone's hand would probably dry within about 30 minutes.
When asked by prosecution counsel Mark Ellison QC about the likelihood of Mr Lawrence's blood being on it if it had remained indoors on the night of the killing, Mr Jarman said: "If the jacket had remained in the wardrobe I can't envisage a plausible explanation for the presence of that stain in the collar."
The court heard that the jacket was first examined by a team at LGC Forensics in October 2007. As part of initial examinations, it was scoured for traces of blood and then sprayed with water as part of a test for saliva samples. The jacket was only re-examined after three fragments of blood with a full DNA match to Stephen Lawrence were found in the folds of the bag in which it was originally held.
Other DNA tests showed that the jacket had been worn by Mr Dobson at some point in the past, Mr Jarman told the court. Testing for blood carried out on a cardigan seized from Mr Dobson's house, and jeans, a sweatshirt and another cardigan taken from Mr Norris's home were inconclusive.
The trial continues.