The Department of Justice has officially launched a so-called "pattern or practice" investigation of the Chicago police department.
To be clear, this investigation is only indirectly related to the killing of Laquan McDonald which is also being investigated. Numerous other incidents, including the operation of a black-site where suspects are held for days without being charged or even officially booked, have prompted this investigation.
From the Associated Press:
"This mistrust from members of the community makes it more difficult to gain help with investigations, to encourage victims and witnesses of crimes to speak up, and to fulfill the most basic responsibilities of public safety officials," [Attorney General] Lynch said. "And when suspicion and hostility is allowed to fester, it can erupt into unrest." [...]
The University of Chicago said last month that an analysis by its civil rights and police accountability clinic found of 56,000 complaints against Chicago police — but only a fraction led to disciplinary action. Among the most notorious cases, dozens of men, mostly African-American, said they were subjected to torture from a Chicago police squad headed by former commander Jon Burge during the 1970s, '80s and early '90s. Burge was convicted of lying about the torture and served 4½ years in prison.
Given the vast size and scope of the Chicago PD it could be many months before we see preliminary results from this investigation but, if the Justice Department determines that local police systemically violate the Constitution, the Chicago Police Department will be required to reform or face a federal lawsuit.
If various reports we've read over the past year are an indication, it seems likely to me that the department is systemically broken. With that said, I believe an investigation of every department in the country would uncover corruption and repeated violations of the Constitution. The Department of Justice can't investigate all of them but it can focus on high profile cases that may set an example for other police departments.
Here's an official statement from the Department of Justice:
During the course of the investigation, the Justice Department will consider all relevant information, particularly the CPD’s policies, training and practices related to using, reporting, investigating and reviewing force. The Justice Department will also look into CPD’s practices related to disciplinary and other corrective action; and its practices related to intake and handling of allegations of misconduct.