The second-largest police force in the United States is under fire again, this time over accusations that its members routinely lie.

Federal prosecutors last month began an investigation in the Chicago Police Department following public uproar over a series of police shootings.

The probe came after a 2014 police video was released in November showing a Chicago police officer shooting a teenager armed with a knife 16 times, including nine times in the back, and following a drove of complaints lodged by city residents, particularly those in the black community.

Officer Jason Van Dyke now faces a first-degree murder charge for fatally shooting Laquan McDonald.

Five officers who witnessed Officer Van Dyke gun down Mr. McDonald indicated that they saw the teenager turn toward the officer before he was shot – video evidence shows that wasn’t true. The death of the 17-year-old McDonald has also brought increased scrutiny to other instances in which police officers made false reports.

In 2014, two officers were caught suppressing evidence that could have led to the release of a man arrested for robbing a liquor store and shooting one person in the leg.

Earlier this year, after another police video emerged, four other officers were charged with perjury for falsely corroborating a story under oath about a traffic stop that uncovered a driver carrying a pound of marijuana.

In October, the Guardian launched a lawsuit against the City of Chicago that exposed a Chicago police station essentially serving as a secret “interrogation warehouse” where police routinely denied legal representation to the mostly African American detainees.

“It is a systematic problem,” said Craig Futterman, an attorney and University of Chicago Law School professor, to Salon. “When there’s a police shooting, or when there’s an allegation of misconduct or brutality, the institutional response is to circle the wagons, denial, and cover up.”

But the federal inquiry could change that.

Federal investigators said in December they will scrutinize claims of pervasive civil rights violations in the department as a whole, rather than against individual officers.

US Attorney General Loretta Lynch said the tactic would be used to improve the system through “training, policy guidance and equipment, to be more effective, to partner with civilians and to strengthen public safety."

More than 20 police departments have been investigated by federal authorities during the last 20 years, a venture that has often forced municipalities and police to move toward reforms.

In May, the city of Cleveland agreed to comprehensive changes to its police force after a US Department of Justice investigation that was launched when officers shot two unarmed black men 137 times in 2012.

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Under the agreement, the federal government will use an independent observer to oversee the Cleveland Police Department and install widespread amendments to how officers use force, according to the Chicago Tribune.

"As we move forward, it is my strong belief that as other cities across this country address and look at their police issues in their communities, they will be able to say, 'Let's look at Cleveland because Cleveland has done it right,' ” Frank Jackson, the city’s mayor, said.