The parents of a shot Florida teenager have accused police of leaking information about their son being suspended from school for marijuana and details about the fight in which he died that portrayed him as the aggressor.

Trayvon Martin's mother, Sybrina Fulton, and family lawyers said yesterday that it was part of an effort to demonise her 17-year-old son, who was shot and killed last month by neighbourhood watch volunteer George Zimmerman.

"They killed my son and now they're trying to kill his reputation," Ms Fulton said.

Trayvon was suspended by Miami-Dade County schools because traces of marijuana were found in a plastic bag in his book bag. He was serving the suspension when he was shot on February 26.

Sanford police department insisted there was no authorised release of the new information but acknowledged there might have been a leak.

Martin family lawyer Benjamin Crump said the link between the youth and marijuana should have no bearing on the investigation into his shooting death. State and federal agencies are investigating, with a grand jury to convene on April 10.

Mr Crump said: "If he and his friends experimented with marijuana, that is completely irrelevant. What does it have to do with killing their son?"