The attorney for the family of Michael Brown, the Ferguson, Missouri teen killed by a white police officer on Aug. 9, said today that an independent autopsy showed he was shot multiple times.

The results come from just one of three separate autopsies that are taking place as part of investigations into the incident, which has sparked ongoing protests outside St. Louis and a strong debate nationwide over the use of deadly force.

The U.S. Justice Department says it will conduct its own autopsy as part of a federal probe into Brown's death. 

So when does the federal government step into local cases like these?

S. David Mitchell, associate professor of law at the University of Missouri Law School, says that the feds often step in when it appears the public has lost faith in local authorities to conduct an investigation properly and that, sometimes, multiple investigations can be at odds.