What Michael Brown’s autopsy can and can’t tell us

AP Photo/St. Louis Post-Dispatch, Christian GoodenChristian Gooden

Last week, forensic pathologists released the first autopsy results in the Michael Brown case. They suggest that Brown, the unarmed black teenager who was killed by police officer Darren Wilson on August 9 in Ferguson, Missouri, was shot six times, all from the front. The fatal wound was likely a shot to the top of the head.

I read about the autopsy reports and was curious whether the findings involved some educated guesswork and, if so, how much. I also wanted to know whether there are any major areas of disagreement in forensic science, places where two experts looking at the same body might reasonably come to very different conclusions about what had happened.

To answer these questions, I spoke with two board certified forensic pathologists with experience conducting gunshot wound autopsies. Their answers to my questions were very similar: Autopsies are nearly unequivocal on some points and on other points—including some with special relevance in the Brown case—they can't tell you much at all.

Take the top-level finding, that Brown was facing the police officer when he was shot. Walter Hoffman, medical examiner for Montgomery County, Pennsylvania, says that to an expert, those kinds of conclusions are relatively easy to draw.

"In 99 percent of the cases [entry and exit wounds] are as clear as day. Some clothing, especially if it's skin tight, can cause an entrance and exit to be mixed up, but that's the exception to the rule."

Kisha Mitchell, director of autopsy services at the Yale School of Medicine, explains that forensic pathologists look for "stippling, little puncture sites around the wound" which suggest an entry wound. She adds that in cases where entry and exit wounds are unclear, it's often possible to sort them out by tracing a bullet's path through the body. The shape of the wound might be ambiguous on the surface of the body, but it can be much clearer when, for example, the bullet passes through the liver.

Another key issue is distance—how far was Dixon from Brown when he pulled the trigger? Here, forensic scientists look for "grease, soot, debris in muzzle or chamber, powder [on the body]," Hoffman says, and can only draw very broad conclusions: "If you're more than 36 inches away, in general you could just as well be 36 feet away or 36 miles away." He also says that from autopsy evidence alone, it's impossible to tell whether someone was backing up or advancing at the time they were shot.

The Michael Brown autopsy results generated a lot of headlines, but will probably won't do much to resolve what actually happened in Ferguson that afternoon.

"Most people will agree this is an entry wound or exit wound, this is the wound track," says Mitchell. "But when you step away from that, you might find five people having five different interpretations on where the person was standing when they got this particular wound."