One of the men accused of murdering Stephen Lawrence appeared "nervous" when quizzed during house-to-house inquiries, a court has heard.
Gary Dobson, 36, was questioned at his parents' home in Eltham, south-east London, three days after Mr Lawrence was killed.
Graham Cooke, then a detective constable, told a jury at the Old Bailey: "In my opinion he was nervous at the time."
Dobson and David Norris, 35, are accused of murdering Mr Lawrence in April 1993, which they deny.
The black teenager was set upon by a gang of white youths in Well Hall Road, Eltham, and fatally stabbed.
In the wake of his death, Mr Cooke conducted house-to-house inquiries including asking Dobson whether he had been at the scene of the murder that night.
The retired police officer told the court: "Dobson said no, he was at home all night studying. He arrived home from college at 5.30pm, that his mother and father were indoors at the time. He said that he did not know the victim, he had heard about the incident from the papers."
The jury was also shown police surveillance photographs of Dobson and Norris outside a house in Bournbrook Road in Eltham, and of Norris outside Southwark Police Station in May 1993, when he attended with his mother.
Dobson was 17 at the time he was questioned and was a student at a college in Covent Garden, central London.
The officer asked him a series of standard questions, and noted that he was around 5ft 9in, slim to medium build with dark brown, short, straight hair, brown eyes and a spotted complexion.