A Nassau officer pleaded guilty last week to causing a crash while he was on duty in his unmarked police car in 2010, then fleeing the scene.

Det. Sgt. William Kaul received a conditional discharge and a $500 fine after pleading guilty to official misconduct, which was the top charge against him. Prosecutors said he quickly drove away after the accident in North Hills on Jan. 2, 2010, disobeyed a superior officer, and parked the damaged police car in the precinct lot in Manhasset before driving home to Scarsdale.

Kaul, 51, a Sixth Precinct officer, had 23 years on the job.

His retirement was effective March 26, 2010, and he is receiving his pension.

"This aberration does not undermine Mr. Kaul's 23 years of exemplary service to Nassau County," said his lawyer, William Petrillo, of Rockville Centre.

Officers sent to Kaul's Westchester home the day after the crash said he showed no signs of intoxication and did not charge him with drunken driving.

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However, sworn statements attached to the criminal complaint against Kaul, given by bartenders at TR's Great American in Williston Park and Edison's Ale House in Manhasset, say that Kaul was drinking beers at those pubs before the crash. The complaint alleges that he was on duty while in the bars.

Police said Kaul rear-ended a Chrysler convertible, which had been disabled on the side of the road, near New Hyde Park Road on the Long Island Expressway north service road. The impact sent the car into a tree and left the driver with back, neck and leg injuries.

According to the court filing, about 15 minutes after the accident, Kaul called a precinct lieutenant and said he was "on his way home." Police said Kaul refused the order of a superior officer to stay at the precinct.