A Seattle Police Department policy that allows officers to invoke their protection against self-incrimination in even the most routine use-of-force investigations is overbroad and offers unnecessary protection to police while undermining public confidence, according to the U.S. Department of Justice.

In a bluntly worded letter Wednesday to Seattle Mayor Mike McGinn, the Department of Justice said the protection has been routinely extended to situations where it was never intended to be applied.

The Department of Justice said the letter was sent in hopes that the department would address the issue immediately, "given the serious nature of our concerns," wrote Jonathan Smith, chief of the Justice Department's Special Litigation Section, and Jenny Durkan, U.S. attorney for Western Washington.

Seattle police spokesman Sgt. Sean Whitcomb said Wednesday that the department had just received the letter and that it was being "carefully reviewed."

McGinn, through a spokesman, issued a similar comment.

The letter focuses on the Police Department's application of a 1967 U.S. Supreme Court ruling called Garrity vs. New Jersey, which holds that any potentially incriminating statement made by a police officer cannot be used to prosecute him in a criminal case if the officer believes he was compelled to give the statement under threat of losing his job.

The law allows for officers, in those cases, to provide a "true and involuntary statement" that cannot be used against them later in a criminal case. Officers often invoke Garrity during internal investigations, when they've been accused of wrongdoing and are forced to choose between being punished at work for not cooperating with the investigation or potentially exposing themselves to prosecution if they do.

The Seattle Police Department, according to the letter, has taken the practice to the extreme, extending the Garrity protection to every use-of-force and officer-involved shooting incident.

"SPD's inappropriate blanket invocation of Garrity may result in the exclusion of important evidence from an investigation," the letter states. "The practice makes it too difficult to quickly exonerate officers who have followed policy, and to properly discipline officers who have not."

The practices also "compromise the ability of prosecutors" to evaluate officer-involved force incidents "and to hold officers accountable for their actions."

Seattle City Councilmember Tim Burgess, who chairs the council's Public Safety and Education Committee, said he found the letter "very helpful."

"It gives the department clear direction in what has been a very confusing environment," he said.

However, he noted any changes in department policy will require negotiations with the Seattle Police Officers' Guild.

According to the Justice Department letter, the recommendations are the result of its ongoing investigation into allegations of the misuse of force and biased policing by Seattle police. The investigation was undertaken last spring at the behest of the American Civil Liberties Union and 34 community groups after a string of high-profile confrontations between police and minority citizens.

It's not clear when the investigation will be completed.

The letter was issued as part of a Justice Department promise to Police Chief John Diaz to bring issues to the department's attention immediately when deemed warranted.

The letter cites the shooting of John T. Williams, a First Nations woodcarver and public inebriate who was killed by Officer Ian Birk in August 2010. The department eventually determined the shooting was unjustified, and Birk resigned.

The Justice Department pointed out that a peer review of the Williams investigation by the San Diego Police Department found the absence of a legally admissible statement "made it impossible to know what Officer Birk saw, how he felt and why he chose to use deadly force."

King County prosecutors later cited their inability to determine Birk's motive as one reason they could not charge him.

The Justice Department is conducting a criminal civil-rights investigation into the shooting.

According to the letter, the Police Department, its attorneys and even its civilian-run Office of Professional Accountability have misinterpreted the law by extending Garrity protection to officers in virtually every instance where force is used, including all shootings. That, the Justice Department said, "is bad policy and goes beyond what is required by law or necessary to protect officers' ... rights" against self-incrimination.

The Justice Department recommended that officers be required to fill out routine use-of-force reports without automatically invoking Garrity.

Justice Department lawyers also point out that the Garrity warning is not found on other reports, log sheets or booking records, "even though those reports could expose officers to the same hypothetical jeopardy."

"In those relatively rare circumstances where an officer might have engaged in criminal misconduct, it is a disservice to the Department, those officers who follow the law, and the community to unnecessarily create artificial obstacles to hold that officer accountable," according to the letter. "SPD's current policies and practices do just that."

Mike Carter: 206-464-3706 or mcarter@seattletimes.com.