It has been five years since a self-help motivational speaker from Long Island hired a man in East Harlem to help him commit suicide and make it look like a murder.

The victim, Jeffrey Locker, was found tied up in his black station wagon on a street in East Harlem. He was 52, a father of three and deeply in debt.

The accused, Kenneth Minor, said Mr. Locker had hired him to “do a Kevorkian” by holding a knife against the steering wheel as Mr. Locker thrust his body against the blade several times.

Since then, Mr. Minor, 42, has been jailed at Rikers Island while his bizarre case has worked its way through the courts. In 2011, Mr. Minor was convicted at trial of second-degree murder and sentenced to 20 years to life. But two years later, an appellate panel threw out the verdict and ordered a new trial, saying the judge had erred in defining assisted suicide to the jurors.

Earlier this year, he was indicted a second time, using the same evidence. This time, the Manhattan district attorney, Cyrus R. Vance Jr., asked a grand jury to add a new charge usually reserved for people who help others commit suicide — second-degree manslaughter — thus making it possible for a jury to consider either option.

Now, in perhaps the final twist, Mr. Minor’s lawyer, Daniel J. Gotlin, said on Monday that his client had reached an agreement with prosecutors to plead guilty, to first-degree manslaughter, in return for a sentence of 12 years. With good behavior, Mr. Minor could be released in as little as five years.

“He wants this to be finished,” Mr. Gotlin said after Mr. Minor made a brief appearance in State Supreme Court before Justice Laura Ward, adding: “He knows he did something wrong. He knows he has to pay a penalty.”

Joan Vollero, a spokeswoman for the district attorney’s office, would neither comment on the plea agreement nor confirm its details. Mr. Minor is scheduled to appear before Justice Ward next week and is expected to enter a plea then, Mr. Gotlin said.

At Mr. Minor’s original trial, the defense and the prosecution agreed that Mr. Locker had hired Mr. Minor to help him die and to make it look like a robbery, so his family could collect life insurance. But they differed on whether Mr. Locker had caused his own death.

Prosecutors said it was a case of murder for hire, even if Mr. Locker had consented to be killed. A medical expert testified for the prosecution that Mr. Minor had repeatedly stabbed Mr. Locker as he lay prone in the car. He later withdrew money from Mr. Locker’s bank account with his A.T.M. card, evidence showed.