HAUPPAUGE - A man who was imprisoned more than 17 years after confessing to the killing of his parents but was recently released when new evidence was uncovered will not face a second murder trial in the case, a prosecutor said on Wednesday.

“It is no longer possible to reasonably assert that the case ... would be successful,” Suffolk County District Attorney Thomas Spota told The Associated Press before publicly announcing his decision.

He said his office will formally drop the indictment against Martin Tankleff in the 1988 deaths of his parents, Seymour and Arlene Tankleff, at a Jan. 18 court conference in Riverhead.

Tankleff, who had quickly recanted his confession, said Wednesday he was grateful and “relieved.”

“I have to thank my family because if it weren't for them I wouldn't have made it,” he told reporters in his attorney's office shortly after hearing the news.

He insisted, “I never should have been charged in the first place.”

He added later: “People who took my life away really should go through the hell I went through for 20 years.”

Spota also announced he will ask Gov. Eliot Spitzer to appoint a special prosecutor to investigate claims made by Tankleff and his defense attorneys that Seymour Tankleff's business associate or others may have been involved in the killings.

The governor's office said it would “carefully consider” the request for a special prosecutor once it has been formally received.

Tankleff, now 36, was convicted in 1990 of killing his parents in their home in the exclusive Belle Terre neighborhood overlooking Long Island Sound.

He was released after serving 17 years of a 50-year term after a New York appeals court found that new evidence uncovered by private investigators suggested the Tankleffs may have been killed in a business dispute.

His case attracted national attention after high-profile lawyers took the appeal amid a public relations campaign by members of the Tankleff family who insisted that someone other than the teenager had killed their relatives.

The panel said it was “probable” that a new jury would render a different verdict if given a chance to reconsider all evidence now available.

It did not find, however, that Tankleff was innocent and instead directed that a new trial be held.

Tankleff was released last week on $1 million bail and immediately started working on what he expected would be his upcoming trial.

Tankleff was convicted of intentional murder in the death of his father but was found guilty of depraved indifference to human life in his mother's death.

Seymour Tankleff was viciously stabbed and left to die in his study; Arlene Tankleff was found bludgeoned in her bedroom.

Spota said Wednesday in an interview in his office in Hauppauge that he opted to drop the charges because the law defining depraved indifference to human life has changed in the ensuing years and could no longer apply to the killing of Arlene Tankleff.

And he said double jeopardy laws prevent him from retrying Tankleff on the intentional murder count for his mother because the 1990 jury acquitted him of that charge.

Without a case against Tankleff in the death of his mother, “the defense will surely argue that all evidence with respect to Arlene Tankleff's murder be excluded from the trial of Tankleff for the murder of his father,” he said.

He said while prosecutors could argue that the evidence be admitted, “I believe that attempting to try half of the case against Tankleff is futile, and I will not do it.”

Tankleff was starting his first day as a high school senior in September 1988 when, he says, he discovered the bodies of his mortally wounded parents. Arlene Tankleff was declared dead at the scene, and Seymour Tankleff was taken to a hospital with critical injuries.

Detectives questioning the teenager falsely told him that his father had awakened from a coma and implicated him in the crime.

“Could I have blacked out ... and done this?” Tankleff said, according to court records. “Could I be possessed?”

“Marty, I think that's what happened to you,” a detective said.

Tankleff then confessed to the killings, according to police, but almost immediately recanted.

For years, Tankleff and his supporters have claimed that the murders were the work of Jerry Steuerman, a Long Island businessman who they said owed hundreds of thousands of dollars to the family and was at the home for a poker game on the evening of the killings.

Within days of the murders, Steuerman faked his own death, changed his appearance and fled to California.

He was never named as a suspect and has repeatedly denied any involvement in the killings.

Steuerman testified as a prosecution witness at Tankleff's trial.

Investigators hired by the defense team tracked down a number of witnesses who claimed to be able to implicate a career criminal, Joseph Creedon, in the killings.

During appeal hearings in the case, Creedon acknowledged that he had a violent past that including working as a debt collector for Steuerman's drug-dealing son, but he said he never killed anyone.

Spota said although the defense theory of a hit being taken out on the Tankleffs is “totally inconsistent” with the evidence, he will ask for a special prosecutor to investigate the claims.

Separately, the state Commission on Investigation has said it will examine the role of police and prosecutors in the case.