Attorney General Eric Holder's visit to Missouri after the shooting death of Michael Brown strongly signaled that he will seek changes at the Ferguson Police Department.
At the time, protesters complained that some police officers had hidden their name tags and were wearing bracelets supporting fellow officer Darren Wilson.
In response, the Justice Department sent two letters to the Ferguson police chief, telling him to make sure officers stash the bracelets and display their IDs.
But bigger changes loom. Civil rights investigators are looking at training, arrest records and use of force complaints to determine if the overwhelmingly white Ferguson police force has demonstrated a pattern of racial bias in the majority black town.
In the past five years, Justice has investigated more than 20 police departments, and ordered corrective actions in at least 15 of them.
In Portland, Oregon, Seattle and Albuquerque, police were cited for excessive force. In Albuquerque alone there have been 40 police-involved shootings since 2010. Now, all three departments have signed agreements to reduce the use of force and tighten oversight.
In East Haven, Connecticut, the issue was racial profiling of Latinos. Now, officers there are subject to enhanced training.
Policing can be improved, as demonstrated by Los Angeles. In 2013, the LAPD completed 12 years of DOJ-mandated changes.
The force, once viewed as overly aggressive, now seeks to defuse confrontations with community outreach. And what was a largely-white department is now 44 percent Hispanic and 13 percent African-American.
"I'm very proud of the way that we reflect the diversity of Los Angeles, and I think that is a significant accomplishment that has occurred over time," LAPD Chief Charlie Beck said.
The changes usually do take a very long time. The DOJ is not expected to wrap up its Ferguson investigation for several months.