Evidence in Trayvon shooting indicates killer was badly beaten

A wealth of newly released evidence relating to the killing of a young black man by a neighbourhood watch "captain" has further muddied the waters in a case that has sparked civil rights protests and gun law debates in America.

Crucial details about the shooting of the Florida teenager Trayvon Martin by George Zimmerman emerged from the nearly 200 pages of documents made public on Thursday night, including that Martin was shot through the heart from point blank range and that the alleged murderer suffered a broken nose and bruises.

The documents also reveal that the lead investigator in the case wanted to charge Zimmerman with manslaughter in the weeks after the 17-year-old's shooting but was overruled.

The new evidence appears to support Zimmerman's contention that he was being beaten up on 26 February this year when he fired the fatal shot.

But the medical examiner's report showed only a small abrasion on Martin's left ring finger and no other injuries – apart from the fatal gunshot wound to the chest – to support Zimmerman's claim that he was nearly beaten to death.

It also bolsters the argument of Martin's parents that Zimmerman was "profiling" Martin (selecting him because of his race) and the confrontation could have been avoided.

Martin had been visiting family in the gated community where Zimmerman lived when he was killed by a single gunshot wound to the heart after a struggle with Zimmerman.

Police initially declined to arrest Zimmerman, citing Florida's "Stand Your Ground" self-defence law.

The decision enraged civil rights campaigners, who held protests across the country and alleged that racial profiling was behind Martin's death.

As demonstrations grew, a special prosecutor was appointed who went on to charge Zimmerman with second-degree murder.

The facts have since been debated on television sets across the country, and stirred feelings of discrimination.

One of the main points of contention in the case centres around a 911 call made by a neighbour reporting a struggle between two men in which the screams of a man can he heard in the background.

Relatives of Zimmerman say the screams are his, and prove he was acting in self-defence, while Martin's parents claim the voice is that of their son pleading for his life.

But Kenneth Marr, a specialist with the FBI's digital evidence laboratory who analysed the tapes, said the recording was inconclusive. "The screaming voice of the 911 call is of insufficient voice quality and duration to conduct a meaningful voice comparison with any other voice samples," he said.

Also among the evidence is the medical examiner's report, which showed traces of THC – the active ingredient in marijuana – in Martin's blood.

An attorney for the Martin family called the marijuana evidence irrelevant, saying it was more telling that police declined to order a drug or alcohol test on Zimmerman.