Thirty years after “Saturday Night Live” star JOHN BELUSHI died from a cocaine-and-heroin overdose, the drug queen who gave him the fatal injection is still tormented by his death – but has never apologized to his widow.

The “Animal House” star was only 33 when he died March 5, 1982, at West Hollywood’s Chateau Marmont hotel. Although his death was initially ruled an accidental overdose, The ENQUIRER tracked down the woman who was with him during his final hours – Catherine Evelyn Smith – and in a world exclusive interview, she told us: “I killed John Belushi.”

The stunning admission landed her in prison, and she’s still suffering remorse.

“Cathy has never gotten over her role in John Belushi’s death,” revealed a friend.

“She has remained guilt-ridden and haunted by memories of that dreadful night. It literally ruined her life. The stigma of causing Belushi’s death follows her everywhere.

“While she has wanted to meet John’s widow Judy to express her sorrow, that meeting has never happened. Judy wants to put the tragedy behind her, and seeing Cathy would only bring back the pain.”

Before The ENQUIRER stepped into the sensational case, the Los Angeles police had decided to end their investigation and released Smith, a Canadian citizen.

But ENQUIRER reporters Larry Haley and Tony Brenna tracked her down in Toronto, and after the bombshell 1982 ENQUIRER interview with Smith, the LAPD reopened the case.

The drug dealer admitted she supplied the heroin used in the heroin-cocaine “speedball” that stopped Belushi’s heart.

She was extradited from Canada on second-degree murder charges. A plea bargain reduced the charge to involuntary manslaughter, and she served 15 months.

Hoping to redeem herself, Smith later lectured Canadian school children on the evils of drugs, breaking down in tears when she recalled the Belushi tragedy.

Despite her anti-drug crusade, Smith was busted in Vancouver in July 1991 with two grams of heroin in her purse.

She was fined and sentenced to 12 months probation.