Miami’s Police Department is one of a number of law enforcement agencies that have been investigated by federal authorities in recent years over abuses like excessive force, racial bias or the handling of sexual assaults. Such investigations usually result in a settlement, known as a consent decree, and the assignment of a monitor to see that changes are made.

Mr. Ferrer noted that this was the second time in a little over a decade that the Justice Department had been called in to investigate the Miami department: the first time was in 2002, when similar problems were found. In a 20-month period after John F. Timoney, formerly of the New York Police Department, became Miami’s chief, no officer discharged a firearm, the report noted. But problems resumed after he left in 2004.

The number of officer-involved shootings in recent years was especially high when compared with that of other big cities like New York and Washington, Mr. Ferrer said. In 2010, he said, there was one fatal shooting for every 4,300 officers in New York, compared with one for every 220 in Miami.

In its report, the Justice Department described “egregious” delays in the investigation of officer-involved shootings by the Miami police; in one case, the officers in a shooting had not provided statements about what occurred more than three years later.

In many cases, officers were returned to duty on the streets while investigations into shootings were still in progress. Officers also showed bad marksmanship and poor judgment, the investigation found, firing their weapons at moving vehicles or when pedestrians were nearby. Specialty units, like those devoted to robberies, gangs, special operations or crime suppression, were involved in a high proportion of shootings: 9 out of 17 total in 2010 and 2011.