Former Nassau County District Attorney Denis Dillon, who in more than three decades on the job prosecuted Long Island Lolita Amy Fisher and the gunman in the 1993 Long Island Rail Road massacre, has died.

Dillon died Sunday from lymphoma at his home in Rockville Centre, just east of New York City, longtime spokesman Ed Grilli said. He was 76.

Grilli said Dillon worked as a top-notch prosecutor, not as a politician, resulting in one of the highest felony conviction rates in the country.

Dillon successfully prosecuted Fisher after she, as a 16-year-old, shot her lover's wife in the head in 1992.

Fisher, nicknamed the Long Island Lolita by tabloid newspapers, visited the home of her much-older lover, car mechanic Joey Buttafuoco, and shot Mary Jo Buttafuoco as she answered the door. She served seven years in prison for the attack.

Joey Buttafuoco, also prosecuted by Dillon, pleaded guilty to statutory rape and served four months in jail. His wife survived the shooting but was partially paralyzed. The couple remained together after the Fisher affair but divorced in 2003 after moving to California.

Dillon also successfully prosecuted Colin Ferguson after he randomly sprayed a crowded commuter train car with bullets from a 9mm semiautomatic gun on Dec. 7, 1993, killing six people and injuring 19.

Ferguson, who represented himself at trial, claimed he was wrongfully prosecuted because he's black. He's serving six consecutive life terms for the massacre.

Dillon first was elected to the district attorney position in 1974 as a Democrat. The former policeman and federal prosecutor, a staunch Catholic, became a Republican in the late 1980s, when the Democrats ramped up their support for a woman's right to an abortion.

He was criticized by opponents charging he was swayed by his religion — as a right-to-life advocate who opposed abortion and personally protested outside abortion clinics. In his office, he kept a picture of the Virgin Mary.

Dillon left office after losing to Kathleen Rice in 2005.

On Sunday, the current Nassau County district attorney released a statement saying she learned of his death "with profound sadness."

Rice called Dillon "a man of integrity, of principle and of tireless commitment" to the community.

"That selflessness spanned the length of his lifelong public service and will remain an inspirational pillar of our office long after his passing," she said.

Dillon, who was born in the Bronx, ran for governor in 1986 as nominee of the Right to Life Party. He served as president of the New York State District Attorneys Association.

His other high-profile cases included the prosecutions of Joel Rifkin, a former landscaper who admitted killing more than a dozen women, mostly prostitutes, between 1991 and 1993, and of Arnold Friedman, who with his teenage son pleaded guilty in 1988 to molesting children during computer classes in the basement of their home in Great Neck, N.Y.

Rifkin, who is serving a life sentence, admitted 17 slayings after his May 1994 murder conviction in Nassau County. He also pleaded guilty to two murders in neighboring Suffolk County.

Friedman, whose sex abuse case was profiled in the Academy Award-nominated 2003 documentary "Capturing the Friedmans," committed suicide in prison in 1995.