A lawyer for Long Island private investigator Joseph Dwyer asked a Manhattan federal judge in papers made public Tuesday to give him probation when he is sentenced Friday for paying an NYPD sergeant to provide confidential information on witnesses.

Dwyer, 47, of Shoreham, a former city cop and the son of a Suffolk officer, was the subject of a Newsday story this week about his role disclosing information about a federal informant in a Bronx exoneration case that federal prosecutors had held back.

The sentencing letter from Guy Oksenhendler, Dwyer’s lawyer, to U.S. District Judge Alison Nathan, filed with redactions, didn’t mention his work with the Bronx district attorney in that case, but said he had for 20 years been a top private investigator devoted to justice for criminal defendants who made a “terrible mistake.”

“It was his overzealousness that led him to [the] case before you,” Oksenhendler wrote.

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The lawyer said Dwyer was “contrite,” but also noted that no information he got was used for improper ends, and quoted a “former counsel” to Dwyer saying that sharing of information among the police fraternity was once common, and that lawyers Dwyer worked for didn’t raise questions about “clearly not authorized” reports.

Dwyer, married with four children, pleaded guilty to conspiracy in January. He faces up to 5 years in prison Friday, but probation officials have reportedly recommended probation. Ronald Buell, the now-retired NYPD sergeant who supplied the information, also has pleaded guilty. No one else is known to have been charged.