(CBS) Crosley Green says that he didn't kill Chip Flynn.
 
On April 3, 1989, 22-year-old Chip Flynn was shot to death in a Central Florida orange grove. Soon after, police arrested Crosley Green, a black man recently released from prison on drug charges. 

On Sept. 5, 1990, all all-white jury convicted Green, then 32, of first-degree murder. He was sentenced to death. Ever since, he has been on death row. 

This year, five prominent private detectives got together to try to exonerate Green. They believe he is innocent. 48 Hours Correspondent Erin Moriarty followed them as they revisited crime scenes, reinterviewed witnesses and reinterpreted evidence, in an effort to save Green's life.

Nine years ago at trial, Green was offered a plea bargain. Had he accepted it, he'd be a free man today. But he didn't take it. 

"I didn't kill that young man," Green says. "So why should I have taken that plea bargain?" 

The fight to clear Green, who is now 41, began in 1996, when he began corresponding with Nan Webb, a 57-year-old white Floridian. Webb, a part-time computer instructor who is also an anti-death penalty activist, became convinced of Green's innocence. 

After corresponding with Green, Nan Webb persuaded Chicago private investigator Paul Ciolino to take a look at the case. When he, too, decided that Green had been railroaded, he 
gathered together four other top private investigators to convince authorities to reopen the case. 

And Ciolino has experience with this kind of case. Earlier this year, he succeeded in having wrongfully convicted Anthony Porter released from Illinois' death row. 

Ciolino believes that men with criminal records - like Green - are often railroaded by investigators pressured to solve cases. 

"We're not a bunch of left-wing, silly liberals running around screaming, 'The poor man is on death row, and we shouldn't kill him,'" he says of the five-man "dream team" of investigators, all working without pay on the Green case. 

"Quite the contrary, most of us are in favor of the death penalty when it's properly administered," he says. 

Webb, though, says that Ciolino has a heart of gold. "He looks like a big old Irish Chicago cop, but inside there is [a] very humble man," she says. "I told Paul that he's an angel." 

"Crosley Green is systematic of the problem we have with the death penalty with this country," Ciolino says. "We're in a rush to judgment to convict people and punish them to make ourselves feel good." 

"This is a feel-good conviction to ease the tension in the community: 'Let's get them off the street. Let's kill them.' And we can all get back to normal," he says. 

One of the main witnesses in the case was Kim Hallock, who was 19 in 1990. She and Flynn, her ex-boyfriend, had gone to Holder Park in Mims, Fla., a little after 11 p.m. to talk. 

She told police that they had been approached by a black man with a gun who robbed and kidnapped them. She said that the gunman had tied Flynn's hands behind his back, and, with Hallock sitting in the middle, had driven Flynn's pickup truck to the orange grove. 

Then, she said, the man grabbed her and forced her out of the truck and onto the ground. Then, according to Hallock, Flynn, who was still in the truck, got his own gun, which Hallock had hidden on the car seat earlier. 

And although his hands were tied behind his back, Flynn came out of the truck shooting, Hallock said. 

Hallock told police that she then got into the truck, drove to a friend's house, and called 911. Within hours, Flynn was pronounced dead at the hospital. 

Police began investigating that night. By morning, they had a suspect: Green, who had watched a baseball game at Holder Park the night before. 

Although Ciolino and his four counterparts are sure that Green is innocent, they have a difficult task. In trying to reconstruct a nine-year-old crime, they have to run down scores of leads and interview witnesses who have changed addresses many, many times. 

Dead ends are just part of the game, says one of the group, Joe Moura, who runs one of the largest detective agencies in the country. "That's what it is; just keep hitting it, keep on hitting it, just like baseball: You strike out here, you strike out there. But every once in a while, you get a single, a double." 

The first break came when they got a witness, Alan "Moon" Murray, to admit that he had lied at Green's trial. 

In 1990, Murray had told the jury that Green had told him that he had killed someone. Now Murray says he lied, because at the time he had been on parole, and he felt pressured by detectives to come up with a story about Green. 

"Man told me if I don't say what they want me to say, I go right back to the slammer," Murray says. The detectives videotaped Murray's confession, but that was not enough to reopen the case. 

The key witness in the case against Crosley Green nine years ago was Green's own sister Sheila. She told the jury that her brother had confessed to her that he had killed Chip Flynn. 

At the time of the trial, Sheila Green had just been convicted of drug charges and was facing a long prison sentence. "I submit to you that Crosley Green's sister at the time would have said Santa Claus committed the murder if that's what the prosecutors told her to say," says Paul Ciolino. 

When Ciolino's team of detectives found Sheila Green, she talked with Paul Ciolino and Joe Moura, but refused to make a videotaped statement. So Ciolino appealed to her family. Shirley Green, Sheila's older sister, persuaded Sheila to allow the detectives to videotape her admission. 

In August, Sheila Green admitted, in a videotaped statement, she had lied at her brother's 1990 trial.  
 
Two days later, Sheila Green publicly admitted that she lied at her brother's trial; she was hoping to exchange the testimony for a lighter sentence. On top of that, the detectives found another witness who said he lied to the jury when he testified that Green had admitted the murder to him. 

At the same time, the detectives followed up on another thread. Nine years ago, Flynn's friend, Tim Curtis, told police that Crosley Green matched the police sketch of the assailant, and that he had heard rumors that Green was the killer. Curtis, who knew him casually, is now a successful auto shop owner who does work for the sheriff's department. Ciolino and his partners did not expect any help from him. 

But they were surprised. Curtis told the investigators that he lied 10 years ago - not because he was pressured but because he wanted to help convict the man he believed killed Flynn. At the time, he says, he thought Crosley Green was guilty. Now, though, he has changed his mind. 

But even four recanting witnesses weren't enough. The detectives began to look at the physical evidence. 

In 1990, the sheriff's investigators had searched Flynn's 1982 Chevy pickup truck; they vacuumed it; they powdered it for prints - and they found nothing: no hair, no fibers, no blood, no fingerprints, no physical evidence to connect Green to the crime. 

There was something else, too, a fact that had been overlooked at the trial. The truck was a manual shift; Green couldn't drive a stick shift, Ciolino says. 

Even if Crosley Green had been a skilled driver, he would have had problems driving this truck, says Curtis, who used to own the truck and sold it to Flynn. "You cannot get in that truck and take off without it stalling," he says. 

Hallock had told police that Crosley Green not only drove the truck and shifted the gears, but also held a gun on his victims. But Flynn's father says that Hallock told him that she, not Crosley Green shifted the gears on the drive to the orange grove. 

Says Ciolino: "Crosley Green, who allegedly abducts [these] people in this truck, drives this truck, shifts this truck, turns the lights on in the truck, is touching the glass on the truck, is touching the right fender, touching the left fender; there is no fingerprints, there is no footprints." 

"Unless Crosley Green is Casper the ghost in disguise, then he couldn't have committed this crime," he declares. 

Curtis is also troubled by this lack of evidence: "You had to grab the truck literally to climb up in it. It wasn't like an automobile. You had to open the door and climb up in it. You couldn't do it without putting your hands on the truck. Impossible." 

The detectives began to raise questions about Hallock's story. "How could you come out of this truck with your hands tied behind your back firing a weapon," Ciolino asked, while looking over the truck. 

Rob Parker, Green's defense attorney, wonders how Hallock was able to identify Crosley Green when the scene of the crime was pitch dark, and she looked at him for less than 30 seconds. 

Immediately after the crime, Hallock told police that although she didn't remember much about the assailant, she knew that he had Jheri-curled hair. At the time, Crosley Green had a buzz cut. 

One juror now says that at the trial, Hallock's testimony sounded like "a made-up story." But Alma Jean Blouse had voted to convict even though she admits now that she had doubts. She felt pressured, she says. 

"The word 'black man' was used in this case at least 60 or 70 times during the trial," Ciolino says. "Black man this. Black man that, Black man this. And all they were interested in communicating to jury was: 'This is your worst enemy'" 

Kim Hallock testified that Crosley Green was the man who shot Chip Flynn.  
 
But Hallock refused to talk to the detectives. In a letter she sent to 48 Hours, she wrote that the "new revelations are insignificant." 

"For the last 10 years, I've had to live with the memories and nightmares of that horrific evening," she wrote. "The fact is there are only two surviving witnesses, myself and Crosley, and I'm sure deep down inside Crosley knows he is right where he deserves to be." 

After three months of work, the detectives decided to offer a $25,000 reward for information leading to the real killer of Flynn. 

State Attorney Norman Wolfinger, who ran the office that prosecuted Crosley Green and who still runs it today, succeeded with his request for an independent state investigation of the case. 

"They're not doing it because they're nice people," Ciolino says. "They're doing it because they were shamed into doing it, because this evidence is so outrageous and so corrupt that they had to do it to keep the faith of the public. They had no choice." 

But what would be a dream for Ciolino, Green and Webb - a new trial - would be a nightmare for Flynn's parents, Peggy and Charlie, who are convinced Crosley Green is the killer. "There's only one side shown," Charlie says. "And that's Crosley Green's. And it's like there's no victim when you only have one side." 

But Ciolino and his four colleagues are still digging. "I want this guy out," he told a Florida reporter last month. "He deserves to be free."