Officer Trey Economidy of the Albuquerque police now realizes that he should have thought harder before listing his occupation on his Facebook profile as “human waste disposal.”

After he was involved in a fatal on-duty shooting in February, a local television station dug up the Facebook page. Economidy was placed on desk duty, and last month the Albuquerque Police Department announced a new policy to govern officers’ use of social networking sites.

Social networking tools like Facebook and Twitter can be valuable assets for law enforcement agencies, helping them alert the public, seek information about crimes and gather evidence about the backgrounds of criminal suspects. But the Internet can also get police departments into trouble.

Public gaffes like Economidy’s — his cynical job description on Facebook was “extremely inappropriate and a lapse in judgment on my part,” he said last week in an email — are only one of the risks. A careless posting on a networking site, law enforcement experts say, can endanger an officer’s safety, as it did in Santa Monica, Calif., last year when the Police Department went to great lengths to conceal a wounded officer’s identity and location, only to have a retired officer inadvertently reveal them on Facebook.

And defense lawyers increasingly scour social networking sites for evidence that could impeach a police officer’s testimony. In one case in New York, a jury dismissed a weapons charge against a defendant after learning that the arresting officer had listed his mood on MySpace as “devious” and wrote on Facebook that he was watching the film “Training Day” to “brush up on proper police procedure.”

In an Arkansas case, a federal appeals court cited as evidence of a police officer’s character photos he posted on MySpace showing him pointing a gun at the camera, flanked by a skull and the legend “the PUNISHER.”

The problem is serious enough that departments across the country are scrambling to develop rules to govern what officers can and cannot do online.

“This is something that all the police chiefs around the country, if you’re not dealing with it, you better deal with it,” said Mark A. Marshall, chief of police in Smithfield, Va., and the president of the International Association of Chiefs of Police, which has developed its own model policy.

His department, Marshall said, has had a few embarrassing episodes. In one, an officer who had been involved in a high-speed chase and ended up in “a little bit of a tussle” with a suspect posted a comment about what a good time he had during the dust-up. In another, an officer posted a photo of a tattoo of St. Michael on her hip. Both were disciplined, Marshall said.

“Unfortunately, you have these extreme incidents that are out there,” he said, “and, candidly, you ask yourself, What on earth were they thinking when they posted that?”

Most social media policies try to balance a police department’s interests against First Amendment protections for the officers. Many include prohibitions against posting any statements that could discredit or reflect badly on a department, that illustrate reckless behavior or that disparage people based on race, religion or sexual orientation. Posting crime scene photos or other evidence from criminal cases online is also prohibited by most policies.

Others go further. Albuquerque’s policy, for example, prohibits officers from identifying themselves as employees of the Police Department or posting photos of departmental insignia — badges, uniforms, cruisers — without permission. And a recent policy by the Police Department in Pueblo, Colo., bans gossiping online with outsiders about department affairs.

Police officials say that the courts have generally upheld restrictions on the speech of government employees when the speech is job related.

“The U.S. Supreme Court has spoken on it so often that the parameters are fairly well defined,” said Martha Stonebrook, senior city attorney in Salt Lake City, who was a co-author of a paper on social networking in law enforcement given at the international police chiefs association’s annual meeting in Orlando, Fla., last year. In one famous 2004 case, the Supreme Court upheld the firing of an officer who filmed himself stripping off a police uniform and masturbating and sold the video on eBay’s adults-only area, using the name Codestud3(AT)aol.com.

But David L. Hudson Jr., a scholar at the First Amendment Center at Vanderbilt University, said the lower courts were still sorting out the implications of the Supreme Court’s decisions involving job-related speech.

“The question of when employees can be disciplined for off-duty speech is hazy,” he said. “Part of our core nature is what we do for a living, and to prohibit somebody from engaging in any kind of expression related to their job is arguably too broad.”

In fact, the Albuquerque policy has met some resistance from the rank and file. Joey Sigala, president of the Albuquerque Police Officers’ Association, said that while the department was entitled to dictate what officers wear and say on the clock, “I don’t believe they have the right to tell us what to do outside of that.”

He said that requiring officers to get permission before posting pictures involving department insignia made it difficult to share news about awards or honors spontaneously with family and friends.

“They’re taking away the ability to demonstrate the good, as well as the bad,” he said.

Chief Ray Schultz of the Albuquerque police said that department officials researched policies from around the nation before developing their own.

“You need to get a handle on this very quickly, because this has the potential to damage the reputation of the organization and also adversely affect you in the courtroom,” Schultz said, adding that some social media sites appeared to be “like the bathroom wall of 20 years ago, except now the entire world can see it.”

His department, he said, has hired a compliance officer to investigate the online presence of any police officer “who comes to the attention of the department,” by examining social network pages and running the officer’s name through Google.

Media coverage is often what prompts a department into action. The Indiana State Police initiated its policy after WTHR in Indianapolis discovered photos of drunken revels on a trooper’s Facebook page. One showed the trooper, Chris Pestow, with a .357 Magnum pointed at his head. He also posted a comment about a homeless man beaten by police officers in California, saying, “These people should have died when they were young, anyway, i’m just doing them a favor,” according to the report by WTHR.

After the controversy, Pestow resigned, said First Sgt. David Bursten, a spokesman for the State Police. He said he instructs new police officers, “Don’t do or say anything that you wouldn’t be proud to have your mother see or hear.”

“That really sums it up,” he said.

Asked about his experience, Pestow said in an email, “A written policy concerning social media from the Indiana State Police prior to my unfortunate misstep would have benefited me considerably.”

Chief Joseph E. Thomas Jr. of the Southfield, Mich., police said that when it comes to social media, it is important for departments to enforce discipline even for small infractions. He cited one instance when an officer photographed goats on a resident’s rooftop before confiscating the animals, then posted the photos. The officer was told to remove the photos from the site and given a verbal reprimand.

“That was cute and it was something that did not harm anybody, but it’s inappropriate,” Thomas said.

He said department officials routinely checked police recruits’ social networking pages when they apply for a job. In one case, he said, a candidate posted this update on Facebook:

“Just returned from the interview with the Southfield Police Department and I can’t wait to get a gun and kick some ass.”

He was rejected.

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