THE FAIRFAX County Police Department has decided to issue some unsolicited advice in a way that should not be part of police procedure. The department is readying cards that officers will hand to victims and witnesses of crimes, advising them that they have the right to refuse interviews by news reporters. If that doesn't strike people as an official warning about cooperating with news-gatherers, the cards add a line for anyone still thinking of sharing news with reporters. Before saying anything, people are asked to call the police: "You will be given advice important to protecting the investigation."

Authorities see this as nothing more than a helpful suggestion. But witnesses, victims and others all too easily could interpret police issuance of the message as a directive. The move appears to be unprecedented, though Fairfax officials say they have received some inquiries from other departments contemplating similar action. They should reconsider. Official "suggestions" such as this one, handed out by officers of the law, have the effect of stretching definitions of police powers and denying citizens appropriate information about crimes.

To its partial credit, the Fairfax County Police Department's public information office has had a policy of trying to contact victims and witnesses at a reporter's request, to see if they would consent to interviews. Spokesman Warren Carmichael notes that this policy will continue, adding that the department's intent is not to shut off information to the public.

But precisely because police departments should not be the sole source of information, they should not be in the business of putting a damper on the willingness of people to share with fellow citizens valuable news about crime.