The Nassau County Police Department has launched an internal investigation into the participation of uniformed police officers in a political endorsement event -- a possible violation of state election law, officials said.

About 10 uniformed officers -- some holding "We Support Kate" signs -- appeared with Hempstead Town Supervisor Kate Murray outside Nassau County Court in Mineola on Monday as the Nassau Police Benevolent Association and the detectives union announced their endorsements of Murray, a Republican, in the race for district attorney.

"The department is reviewing the actions of the officers to determine if any violations of the Nassau County Police Department rules and regulations occurred," department spokesman Insp. Kenneth Lack said in an email Wednesday.

ColumnNassau cop unions promote Murray for new ballot lineColumnNassau PBA backs Murray for DA

It's unclear what department rules say about officers' participation in political events. The department declined to provide its policy.

Police officers, like other citizens, have a constitutional right to engage in political activities. But, a recent state Board of Elections opinion said: "A police officer may not endorse a political candidate, either verbally or by his or her appearance at a campaign event, while in uniform, or similarly may not deliberately or knowingly appear in any political communication . . . while in uniform."

The April 30, 2014, opinion adds: "The use of the uniform as a prop adds the weight of the police office to the endorsement and accomplishes the very evil which . . . [the election law] would avoid."

advertisement | advertise on newsday

Nassau PBA president James Carver said Tuesday he was unaware of the law.

"We've been doing that for probably 20 or 30 years, and nobody's ever said anything to us," said Carver, adding that officers at Murray's rally were off-duty. "We've done it for both sides -- Republicans and Democrats alike. . . . I think it's much ado about nothing."

Carver pointed to a 2013 re-election campaign commercial for then-Nassau District Attorney Kathleen Rice, a Democrat, which featured uniformed officers. Rice's spokesman declined to comment Wednesday.

Carver added: "Obviously, if it's something in violation of the law, then we would comply with the law."

Murray's campaign spokesman did not respond to a request for comment. A spokesman for acting District Attorney Madeline Singas, a Democrat who is running against Murray, declined to comment. Her campaign did not respond.

James Gardner, interim dean at the University at Buffalo law school, said prohibitions on uniformed officers expressing political sentiment have a "very ancient" history and come from "the fear that . . . a show of official force conveys a very inappropriate message of official government endorsement of a particular candidate."

Violations often go unchecked, he said, because "election laws are among the most poorly enforced laws on the books."

Thomas E. Connolly, a state elections board spokesman, said the election law statute cited in the 2014 opinion is more than 40 years old.

advertisement | advertise on newsday

"The opinion from last year arose out of a couple of complaints that were filed with the board that sought clarification," Connolly said in an email.

He referred questions to the board's independent compliance unit created by the State Legislature in September in response to criticism of election board enforcement.

A compliance official said by email: "All complaints are confidential and the public is encouraged to report violations."