Former Black Panther leader Marshall "Eddie" Conway walked free Tuesday after spending four decades behind bars for killing a Baltimore police officer — making his one of the highest-profile cases affected by a high court decision that has cut short prison sentences for dozens of felons in recent years.

Conway, now 67, always said that he was innocent, alleging political motives in the prosecution of a 1970 shooting that killed Officer Donald Sager, 35, and injured another officer. Over the years many supporters, including prominent Baltimore politicians, have joined his cause.

Police union officials and Sager's family said they still believe Conway was guilty. But prosecutors — faced with the prospect of retrying a more than 40-year-old case built on the testimony of a fellow police officer and a jailhouse interview — said they could not have convicted him again.

Conway sought a new trial under a 2012 decision by the Maryland Court of Appeals, which said verdicts before 1980 were invalid because of faulty jury instructions. Under a deal with prosecutors, Conway agreed to abandon his court fight in exchange for his release on time served.

Conway walked out of the courthouse about 3 p.m. and then went to a friend's house to eat a plate of vegetable lasagna with his two sons and other supporters, according to Dominique Stevenson, a longtime advocate who co-wrote a book with him. Conway declined to be interviewed.

"He's just taking it all in," Stevenson said.

Supporters have long believed that Conway was set up because of his role with the Black Panthers, and on Tuesday the Baltimore branch of the National Association for the Advancement of Colored People and others hailed his release, calling it a "monumental day" and "an important page turner in this tragic story."

But Sager's son, who was 7 at the time of his father's death, said he was devastated. David Sager said he was warned of the outcome more than a month ago in a meeting with Baltimore State's Attorney Gregg L. Bernstein.

David Sager said he debated whether to attend Tuesday's hearing. He decided against it.

"My mother passed away two years ago, and in a way I'm glad that she's not around to see this," he said. "This is a very sad day. I think this is another tragedy on our justice system, one of a string of tragedies."

Police union officials said they were troubled by the release. Gene Ryan, vice president of the city's Fraternal Order of Police lodge, said it was "difficult" to learn that Conway would not serve out his life in prison.

He blamed the appellate courts for creating the circumstances that have led to Conway and others winning release.

Since the 2012 ruling by Maryland's highest court, dozens have fought their convictions and prosecutors have made deals to release many of them, opening old wounds for victims' families.

In Conway's case, Bernstein said that dealing with someone convicted of killing a police officer created "a different set of issues and concerns."

Bernstein did not believe prosecutors would have been able to convict Conway in a retrial after so many years. "It's about ... whether there's sufficient evidence to convince 12 people beyond a reasonable doubt that he committed this crime," he said.

Bernstein said his office reviewed the case carefully and explained the legal hurdles to Sager's relatives, whom Bernstein described as "accepting and comfortable with the result."

David Sager recalls it differently. "He rolled over," Sager said of Bernstein. "He didn't put up a fight. I can't stress it enough, that it's a dark day."

Conway grew up in West Baltimore and joined the Army at age 18. When he returned from a tour of duty, he went to work for Johns Hopkins Hospital and got involved in civil rights work, eventually joining the Black Panther Party and taking a leadership role as it began a Baltimore operation.

But in 1969 he began to suspect that the chapter had been organized by a government infiltrator working for the National Security Agency, and met with national Panther leaders to make plans to purge infiltrators.

Those plans were in motion, Conway said, when on April 24, 1970, authorities said Sager and Officer Stanley Sierakowski arrived in the 1200 block of Myrtle Ave. to investigate a purported domestic disturbance. Gunfire broke out after they returned to their car. Sager was found dead in the cruiser and Sierakowski lay wounded in the street.

Two men — Jack Ivory Johnson, 23, and James E. Powell, 35 — were found hiding under the steps of a home during a police manhunt. Police concluded that Baltimore's Black Panthers had orchestrated the ambush as an initiation for new members and that Conway had led them in the attack.

The prosecutor in the case said the motive was no theory: "That was Jack Ivory Johnson's confession," former Assistant State's Attorney Peter Ward recalled in a 2001 interview. "He said he and Powell were interested in joining the Panther Party and that the rite was to 'off a couple of pigs.'"

Crucial to Conway's conviction was testimony by a police officer, Roger Nolan, who said he exchanged gunfire with Conway in an alley near the shooting scene. The state's case also relied on a jailhouse informant named Charles Reynolds, who testified that Conway detailed the crime to him as they sat together in a cell, including a little-known detail about a watch stolen from Sierakowski.

But Conway's supporters countered that the evidence was circumstantial and that the jailhouse informant could have lied.

Supporters have focused on the idea that Conway was set up. The Panthers at the time were under surveillance by the Counter Intelligence Program, or COINTELPRO, a group of federal and local law enforcement agents whose mission was to "neutralize" organizations deemed subversive.

In 2001, the Baltimore City Council, including now-President Bernard C. "Jack" Young, passed a resolution urging Gov. Parris N. Glendening to pardon Conway, calling him a political prisoner innocent of murder. Through a spokeswoman, Young declined to comment Tuesday night.

NAACP chapter President Tessa Hill-Aston said the organization does not discount the fact that a police officer lost his life in the 1970 shooting. But she said Conway's prosecution came during an era in which black leaders were targeted by government officials to silence them.