Months before Freddie Gray died of the broken neck he suffered during what Baltimore's top prosecutor called an illegal arrest, city officials asked the Justice Department for help addressing misconduct by officers.

The voluntary review is one step cities with troubled police departments can take to head off a full-scale civil rights probe. But in the wake of Gray's death, critics are wondering whether city leaders are capable of implementing the change Baltimore needs without direct, intensive federal oversight.

Mayor Stephanie Rawlings-Blake has already pushed back against the possibility of a federal civil rights investigation, which usually results in a consent decree. But experts say federal oversight has been effective in many other cities.

A consent decree would also be expensive for the cash-strapped city.