Earlier this spring, a Baton Rouge police officer snapped a photo of a supervisor apparently sleeping on the job and sent it to the Mayor-President’s Office using an anonymous email address. The image stirred up some trouble, Baton Rouge police said.

So when a second photo of a different cop apparently sleeping in a squad car landed in the mayor’s inbox a few days later, again sent anonymously, authorities took action, thinking another cop was misbehaving, police said.

The tipster, as first reported Monday by WBRZ-TV, was not a cop. And the resulting internal investigation raised questions about the police’s response to the incident, especially in light of the issuance of a search warrant in May seeking the phone records and identity of the tipster. The fact that police sought the warrant looking for evidence of criminal defamation — a state law ruled unconstitutional on several occasions in the past 50 years — only increased the flames fanning the controversy.

As it turned out, the search warrant was useless to police and the tipster was never cited for violating the law. Police ended up finding the tipster through social media, using his email address as a starting point for the search and speaking to him not long after the internal investigation began, said Lt. Jonathan Dunnam, an assistant commander of the department’s Internal Affairs division at the time of the incidents.

The police investigated the second tipster so vigorously, police said, only because the informer in the first complaint turned out to be a cop who was violating department policy by sharing with city-parish officials the photo of his supervisor, who appeared to be sleeping.

The department wanted to make sure the second case also wasn’t spurred by a tip from an officer, said Sgt. Mary Ann Godawa, a police spokeswoman.

“It just came right on the heels of the first one,” Godawa said.

The photo sent by the non-police tipster was a screen-grab of an image showing one smiling officer taking a picture of himself with another officer looking asleep in the other seat of a police car. The officers told internal investigators that the selfie was intended as a joke, and that the officer wasn’t really sleeping, according to the search warrant.

The officers were counseled about violating departmental policy. But police still wanted to find out the source of the tip.

To do so, they issued the search warrant on May 29 for evidence of criminal defamation concerning the anonymous tip. State District Judge Tony Marabella approved the search warrant.

Police said they also sent the tipster an email warning him that if he was a police officer, he may have violated department policy by sharing the anonymous photo. And if he wasn’t a police officer, he might be in violation of the state’s law against criminal defamation, which makes it illegal to maliciously publish or express anything that might expose the defamed person to hatred, contempt or ridicule.

But criminal defamation has been ruled an unconstitutional law on several occasions, most recently in February by U.S. District Judge Shelly Dick in a case involving a former Livingston Parish road inspector. Royce McLin, the former inspector, claimed the Livingston Parish Sheriff’s Office and several parish council members violated his civil rights by colluding to accuse him of making derogatory statements about the council members through an anonymous Facebook account.

In her ruling in February, Dick said deputies may have violated McLin’s Fourth Amendment rights when they seized computers and video game consoles from his home in June 2012 to determine if McLin wrote the comments on Facebook. Dick said deputies were searching McLin’s home for evidence of a crime that has been found to be unconstitutional and unenforceable.

“Plaintiff argues that it is objectively unreasonable to seek, obtain and thereafter execute a search warrant to seek evidence of the commission of a ‘crime’ that is, in fact and as matter of long settled law, not a crime,” Dick wrote in her ruling. “The Court agrees.”

Craig Freeman, a media law expert and former LSU professor, described the state’s law against criminal defamation as unconstitutional for the most part.

However, he acknowledged that the police photo case may not fit perfectly under previous rulings because this one involved someone who wasn't a public official as the target of the alleged defamation. Although the police officers are public employees, they would not be considered public officials, Freeman said.

When the target of the defamation is a public official, as in previous cases, the Louisiana law is definitely unconstitutional. Even so, Freeman said he doubted the difference in this case would make a difference in the constitutionality of the law.

But Freeman doubted the detail would make a difference in the constitutionality of the law.

“It’s just not constitutional,” he said.

He described it as “troubling” that Marabella signed the warrant, and Freeman also questioned why the police department has not done more to educate its officers about the constitutionality of the law.

As long as legislators don’t repeal the law, though, the department will continue to enforce it as they would any other state law, said Godawa, the police spokeswoman.

“If it’s on the books,” she said, “we’re going to enforce the law.”

Editor's note: An earlier version of this story incorrectly explained the differences between the alleged defamation case against the two police officers in the picture compared to previous defamation cases in Louisiana ruled unconstitutional. The article said most of the previous cases involved public officials making the allegedly defamatory statements. In fact, it was because public officials were targets of the alleged defamation in those cases that set this case apart from most of the others. The two police officers in the picture likely would not be considered public officials.

Follow Ben Wallace on Twitter @_BenWallace.