A suspect in the murder of the black teenager Stephen Lawrence claimed yesterday that "nine years of persecution" after the killing led him to "flip" and throw a drinks carton at an off-duty black police officer.

David Norris, 25, told a jury that he threw the McDonald's container at Detective Constable Gareth Reid because the officer had given him a "certain look" as he crossed a road in front of him.

Mr Norris, together with Neil Acourt, 27, another suspect in the Lawrence killing, is accused of committing a racist attack on Mr Reid by shouting the word "nigger" as they drove past him. The incident took place in May last year outside a railway station in Eltham, south-east London.

The racist abuse was allegedly shouted at the policeman by Mr Norris, from Chislehurst, Kent, as he threw the drinks container. Mr Acourt, from Greenwich, south-east London, is said to have laughed hysterically. Both men deny a joint charge of racially aggravated harassment intended to cause alarm or distress.

Mr Norris told Woolwich Crown Court that an alleged campaign of threatening letters to his family since Stephen Lawrence was murdered by a white gang in 1993 had caused him to lose his temper when he saw Mr Reid.

He said: "Mr Reid was looking at us in a certain tone, with a certain look on his face, like he was not really appreciating us being there."

The jury is expected to retire today to consider its verdicts.