Prompted in part by the fatal shooting of a deaf woodcarver by a Seattle police officer, the Department of Justice has launched a probe of the agency to determine if officers are using unneccessary force.

The DOJ announced Thursday it would open a "pattern or practice" investigation into allegations of excessive force and discriminatory policing by Seattle Police officers. The probe was requested by the ACLU of Washington, who cited six examples of excessive force in a Dec. 3 letter to U.S. Attorney Thomas Perez .

Chief John Diaz told the Seattle Times he welcomed the investigation as a "free audit."

The most recent high-profile incident involved Seattle Police Officer Ian Birk , the officer who fatally shot carver John T. Williams in August. King County prosecutors elected not to pursue charges against Officer Birk, who resigned from the force after an internal investigation found the shooting unjustified.

The ACLU's letter also references a June jaywalking incident involving Officer Ian Walsh , who was exonerated for punching a jaywalker as a group surrounded the officer and taunted him.

In October 2010, a convenience store camera captured a plainclothes officer kicking a 17-year-old.

Also, officers were captured on video confronting a robbery suspect in April of 2010. While the man was laying prone on the sidewalk, an officer kicked him in the face and threatened to beat the "Mexican piss" out of him.

The investigation's legal foundation derives from the Violent Crime Control and Law Enforcement Act of 1994, the anti-discrimination provisions of the Omnibus Crime Control and Safe Streets Act of 1968 and Title VI of the Civil Rights Act of 1964.

Related:

Video: Seattle PD Releases Dash-Cam Footage of Homeless Carver Shooting

Seattle Officer Cleared In Punching of Jaywalker