Expert weighs in on Michael Brown autopsy

While a grand jury decides whether to indict Ferguson police officer Darren Wilson in the shooting death of Michael Brown, leaks in the process have given the public a look at some of the evidence presented by prosecutors.

Dr. Lawrence Kobilinsky, a professor at John Jay College of Criminal Justice and an expert in forensics, examined the official autopsy performed on Michael Brown's body by Missouri authorities and shared his thoughts with CBS News.

Kobilinsky said the key pieces of evidence from the autopsy were the number of rounds that hit Brown's body as well as the trajectories of those bullets.

"The trajectories of these wounds to the body tell us the relative position of Michael Brown to police officer Wilson," Kobilinsky said.

Brown suffered a graze wound to the right hand, near his thumb. Particulate matter in the tissue is "consistent with gunshot residue," according to the autopsy.

"That tells me that that right hand was very close to the gun when it went off," Kobilinsky said. That may support Wilson's version of events that there was a struggle at the police car between he and Brown that led to the shooting.

However, a private autopsy commissioned by Brown's family found that there was no gunshot residue on Brown's body. Brown's family believes that the 18-year-old was shot from a distance while trying to surrender, an account supported by some witnesses.

The nature of the first bullet wound to Brown's right forearm, as detailed in the official autopsy, casts doubt on the claim of surrender, according to Kobilinsky.

"If one is in the process of surrendering, one's palms are forward," Kobilinsky said, adding that the bullet would enter on the underside of the arm. However, the round entered on the other side of Brown's arm.

"People don't give up, they don't surrender with their palms facing in. So for that round, I think the simplest explanation is the arms were down, rather than up."

Even here, though, there is conflicting data that underscores the challenge of reaching a definitive conclusion: another round hit Brown's arm from the exact opposite trajectory.

"That for me is hard to interpret, and I think that different pathologists may reach different conclusions," Kobilinsky said.

The wounds to Brown's head also lend themselves to multiple versions of events.

One of the rounds that entered Brown's skull near his right eye came out of his right jaw, which means the bullet traveled down and to the right through the head. According to Kobilinsky, that suggests Brown's head was facing down.

"You can postulate he was in the process of falling when those shots were fired or he was charging at the police officer, which is consistent with what police officer Wilson alleged," Kobilinsky said.

The grand jury's decision on whether to indict Wilson is expected to be released in the coming days.