(CBS) SANFORD, Fla. - Although the trial of George Zimmerman, the neighborhood watch volunteer charged with murdering Trayvon Martin is still months away, the investigation into what happened the night of shooting is on-going. New details emerged on Wednesday regarding the condition of Martin's body. Wounds found on the 17-year-old's knuckles may support George Zimmerman's claim that the unarmed teenager assaulted him before he was fatally shot,.
A responder at the crime scene told CBS News that he and others saw wounds on the knuckles of one of Martin's hands as he lay dead on this lawn. This suggests that Martin had thrown a punch.
Zimmerman told police he fired the shot at point blank range while on his back, as the 17-year-old straddled him. He also told investigators Martin did not die immediately but mumbled either "it's over" or "you got me."
State crime analysis of Martin's clothes includes gun powder residue which could indicate the distance between the men.
Meanwhile, special prosecutor Angela Corey's team collected evidence including two surveillance videos. One video was from the 7-11 where Martin bought Skittles and an ice tea while the other was from the clubhouse in the gated subdivision where Zimmerman shot him, according to CBS News.
The case also includes Zimmerman's medical report the day after the shooting, which listed a broken nose, two black eyes and a cut in the back of the head.
A source also told CBS News an unreleased police report noted Zimmerman's sweatshirt had "grass stains, and was wet on the back."
Details from Trayvon Martin's autopsy show the bullet entered the left side of his chest and shattered the ventricle, one of his heart's two large chambers, but the round did not leave his body.
The medical records were part of the evidence that prosecutors have in the second-degree murder case against Zimmerman. He has entered a plea of not guilty and claims self-defense in the shooting.