A police sergeant linked to the still unsolved murder of his common-law wife was charged in a tangled housing fraud scam, according to an indictment unsealed in federal court yesterday.

The sergeant, Martin Peters, 41, was charged for three housing-fraud schemes: illegally accepting a rental subsidy from the department of Housing and Urban Development, falsely reporting his income in bankruptcy papers, and obtaining citizenship through a sham marriage.

According to the indictment, Mr. Peters, a 10-year NYPD veteran working in the Manhattan Courts section, was living in the subsidized apartment at Manhattan while earning well above the low-income limits. The apartment had initially been rented under the federal housing program to Mr. Peters’s mother, Claudette Peters, 58, and her husband, Alfred Peters, 68, who live in another rent-stabilized apartment at Brooklyn.

The financial schemes were in part found, according to the indictment, among bankruptcy papers Mr. Peters filed in January 2003, when he claimed to have racked up $79,000 in credit card and other forms of debt.

Instead of paying $859 in monthly rent for a Manhattan apartment, Mr. Peters, who at the time was living with a new wife, was paying the HUD-subsidized rent at the apartment, $286 a month.

If convicted on the housing subsidies fraud charges, Mr. Peters and his parents could face a maximum 10-year prison sentence and a maximum fine of $250,000 a piece, police said. Mr. Peters also faces additional prison time and fines on other charges. An attorney representing Mr. Peters and an attorney representing his parents could not be immediately reached yesterday.

Yesterday’s indictment came during an ongoing probe of the sergeant by the police department’s internal affairs division. Officers from that division questioned him in the murder of his common-law-wife, Juliette Alexander, a 29-year-old guard for the Immigration and Naturalization Services, who was found dead in her Brooklyn apartment in January of 2001. Alexander, who had given birth to two children by Mr. Peters, had suffered several gunshots to the back of the head.

A childhood friend of Mr. Peters, Nigel Callender, was also shot inside the Brooklyn apartment, and recovered from his injuries. After the shootings, Internal Affairs investigators asked Mr. Peters to surrender his badge and gun and he was placed on desk duty.

Police Commissioner Raymond Kelly, said yesterday that Mr. Peters was still “a person of interest” in the murder case, but not a suspect.