NEW YORK – For almost two decades, Barbara Kogan shook off the suspicion that shadowed her soon after her estranged husband was shot dead outside his mistress’ apartment.

Authorities had ample reason to wonder whether she was involved. The couple was in the throes of a harsh divorce, and she collected about $4.3 million in life insurance after his death.

But even after she was indicted and her accused accomplice convicted, the widow insisted she had nothing to do with real estate tycoon George Kogan’s 1990 death — until this spring. She pleaded guilty to orchestrating a contract killing prosecutors say was driven by jealousy and greed.

Barbara Kogan, 67, offered no explanation or apology as she was sentenced Friday to up to 36 years in prison; she must serve at least 12.

Kogan ultimately pleaded guilty to manslaughter and other charges after learning that prosecutors had tapes of her making incriminating remarks to a friend on a jail telephone, defense lawyer Barry Levin said, adding that she also wanted to spare herself and her family the anguish of a trial.

She has been diagnosed with bipolar disorder and has been hospitalized repeatedly, including three times in the past five years, he said. “I don’t say this to excuse this crime … but I bring that out because I don’t think that Barbara Kogan had or has the capability today to think through all of her actions,” Levin said in court.

The scion of a wealthy family that owned department stores in Puerto Rico, George Kogan for a time owned a San Juan resort and casino, among other properties. After moving to New York in 1987, the Kogans bought a Fifth Avenue apartment and opened an antiques store, Kogan & Co.

Then the marriage faltered, and George Kogan left her for a woman 20 years his junior: Mary-Louise Hawkins, a publicist the couple had hired to promote the antiques business.

As the two hashed out a divorce, Barbara Kogan became consumed with a hunger for money — especially after a judge turned down her request for $5,000 a week in alimony — and bitterness at her husband’s new love, said Assistant District Attorney Joel Seidemann.

Meanwhile, Kogan met Manuel Martinez, a lawyer who would later be convicted of helping her hire a hit man.

A week before the shooting, she called the couple’s life insurance company to confirm she was the sole beneficiary of her husband’s policy, one of the company’s lawyers testified at Martinez’ 2008 trial. Then Kogan and Martinez flew to Puerto Rico and borrowed $100,000 to pay a contract killer, Seidemann said.

Despite collecting the life insurance money, Barbara Kogan filed for bankruptcy in 1998.

“The real irony is that in having George (killed), Barbara Kogan lost the one person who understood that she was in need of special care, and who tried all of their married life to indulge her material desires and keep her safe,” Hawkins wrote in a letter to the court read Friday.

No gunman has ever been charged, although prosecutors have identified a suspect who is imprisoned on unrelated charges. He denied killing Kogan in a 1998 newspaper interview.

Martinez, 60, was convicted of charges including murder, although he maintained his innocence even at his sentencing. He’s serving 25 years to life in prison.

Information that emerged at his trial helped prosecutors build their case against Barbara Kogan, and she was indicted about seven months after his conviction.