BALTIMORE — Baltimore police officers routinely discriminate against blacks, use excessive force too often and are not adequately disciplined for misconduct, according to a harshly critical Justice Department report being issued Wednesday.

The report, the culmination of a yearlong investigation into one of the country’s largest police forces, also found that officers make large numbers of traffic stops – mostly in poor, black neighborhoods – with dubious justification and unlawfully arrest citizens for making speech deemed rude or offensive.

Justice Department officials were expected to make their findings public at an event in Baltimore on Wednesday.

The report is a damning indictment of how officers carry out the most fundamental of policing practices, such as traffic stops and searches and responding to First Amendment expression. But it could also serve as a blueprint for change and could force the department to commit to sweeping changes in order to avoid a federal lawsuit.

The federal investigation was launched after the April 2015 death of Freddie Gray, a 25-year-old black man whose neck was broken while he was handcuffed and shackled but left unrestrained in the back of a police van. The death set off protests and the worst riots in decades. The report examined a slew of potentially unconstitutional practices, including excessive force and discriminatory traffic stops, within the department.

Federal investigators spent more than a year interviewing Baltimore residents, police officers, prosecutors, public defenders and elected officials, as well as riding along with officers on duty and reviewing complaints.

State’s Attorney Marilyn Mosby, the city’s top prosecutor, said she expected the report to “confirm what many in our city already know… .”