NEW YORK — Dr. John Chase Wood Jr. was shot in the heart for $5 in his wallet in 1981, walking back to work at a hospital after dinner with his pregnant wife. The 31-year-old pediatric surgeon-in-training died as weeping colleagues tried to save him in his emergency room.

Wood’s killing became a symbol of a violent era’s senseless street crime — and a case that lingered unresolved for more than two decades. One suspect was acquitted; the second, Daryl Whitley, was convicted, but not until his second trial in 2002.

But last week a judge threw out Whitley’s conviction, saying jurors should have been told that the key prosecution witness had tried to back off his testimony. The ruling opens a chance at freedom for Whitley, 47, who has maintained his innocence. And it reopens questions and wounds that prosecutors, police and the doctor’s family had considered, at long last, closed.

“John will always be a part of my life because we have a son and a grandson. I’m not going to forget,” said his widow, Dr. Diana Newton Wood, now an anesthesiologst living in her her native Sudbury, Mass., who remarried and had two more sons. “But to have to constantly retry it in the courts — it’s discouraging.”

Manhattan prosecutors said they plan to appeal the ruling, which gives them two months to decide whether to release Whitley or retry him. He has said he was framed by a series of jailhouse informants.

“It was injustice, but now we got justice,” said Whitley’s wife, Tammy Futch.

Wood was accosted on an upper Manhattan street on Nov. 2, 1981, by two men who demanded prescription drugs and money. One drew a gun and shot him.

The city was used to a high crime rate, logging almost four times as many murders in 1981 as last year. Still, New Yorkers were stunned by the doctor’s slaying and moved by the plight of the 24-year-old nurse he had married only about five months before.

Detectives initially interviewed hundreds of people, but the trail went cold until 1994, when a detective arrested a man he had long suspected of being the gunman, Patrick McDowell. Whitley was arrested a year later.

Jurors deadlocked during McDowell’s first trial and acquitted him in 1997.

With no physical evidence or eyewitnesses, Whitley’s prosecution rested heavily on four jail informants who said Whitley had made incriminating statements to them.

One longtime acquaintance, Glenn Richardson, agreed to testify against Whitley as part of a plea bargain in exchange for a reduced sentence in a drug case that could have sent him to prison for 20 years to life.

At Whitley’s first trial, Richardson testified that Whitley told him he and McDowell were “looking for somebody to rob, and the doctor came along, and (McDowell) shot him.”

Jurors deadlocked.

By the time of Whitley’s retrial, Richardson was out of prison and told a judge he “was not clear and conscious” when he initially told police about Whitley’s alleged remark. Through a lawyer, he added that he’d never been sure Whitley admitted taking part in the robbery and shooting.

Told he could face perjury charges, Richardson invoked his Fifth Amendment right against self-incrimination and refused to testify again.

His earlier testimony was read to jurors at Whitley’s second trial, leading to Whitley’s 2002 conviction. He was sentenced to 22 years to life in prison.

In his ruling last week, U.S. District Judge Alvin Hellerstein said Whitley hadn’t gotten a fair trial because jurors didn’t know about Richardson’s attempt to recant.