SEATTLE – The Washington State Bar Association is asking the state Supreme Court to ban police from posing as lawyers – as officers did to obtain DNA evidence in one recent case – saying the practice is unnecessary and damages the credibility of attorney-client relationships.

The issue arose following the conviction of John Athan, a Palisades Park, N.J., man found to have murdered a 13-year-old girl in Seattle in 1982, when he was 14. Though Athan was a suspect in the case, police didn’t have the evidence to arrest him, and the case went unsolved for two decades.

In 2003, police sent him a letter on the stationery of a fictitious law firm, asking if they could represent him in a class-action lawsuit. Athan licked the envelope and returned it, providing the DNA sample investigators needed to link him to semen found on the girl’s body.

Athan was convicted of second-degree murder last year and sentenced to at least 10 years in prison. The state Supreme Court has agreed to hear arguments in his appeal next month, and the bar association planned to file a “friend-of-the-court” brief Wednesday asking the court to rule against police impersonating lawyers. The issue is central to Athan’s appeal.

“Persons who consult with a lawyer justifiably expect that they are interacting with their counselor and advocate,” the bar association wrote in an outline of its brief. “The police actions in this case were gratuitous. Any number of alternative ruses could have achieved the same result without unnecessarily creating – and abusing – the attorney-client relationship.”

Forcing clients or potential clients to research for themselves whether lawyers they’re dealing with are truly lawyers could have a chilling effect on attorney-client relations, Bob Welden, head of the bar’s amicus committee, said Tuesday.

It’s against the law in Washington to practice law without a license, an offense that is a gross misdemeanor for the first offense and a felony for subsequent offenses. During Athan’s trial, police and prosecutors argued that law-enforcement officers can occasionally break the law while investigating crimes, such as when undercover agents buy drugs from dealers.

King County Prosecutor Norm Maleng urged the bar association not to get involved in the case.

“Working to free a convicted killer should never be the goal of the mandatory bar that purports to represent all lawyers in this state, including prosecutors,” Maleng wrote in a letter to the bar association, adding that Athan’s appeals lawyers would make that argument capably enough on their own.

Athan’s lawyer, John Muenster, wrote back, “I for one do not believe the fundamental principles of our legal system should be sacrificed for the sake of upholding a single person’s conviction.”