A group of high-profile US lawyers and justice campaigners have launched a bid to clear the name of a prisoner executed 10 years ago in Missouri.
Larry Griffin said he was innocent until the end
The campaigners say there is enough new evidence to prove Larry Griffin was innocent of murder.
Attorney Jennifer Joyce re-opened the case on Monday, at the request of law experts studying the case.
Analysts say the evidence provides the strongest case yet that a man may have been put to death by mistake.
If Griffin is found to be innocent, the case could have an effect on US public opinion, which currently broadly supports capital punishment, they say.
Griffin was convicted in 1981 for the drive-by shooting of Quintin Moss a year earlier.
He maintained his innocence right up until his execution, on 21 June 1995.
'Jury was right'
His cause has now been taken up by Democrat Congressman William Lacy Clay and lawyer Barry Scheck, co-founder of the Innocence Project, a group which works to re-open cases of possible wrongful convictions.
"What I have heard recently is very troubling and leads me to believe an innocent man was executed for this murder, while the real killers have not been brought to justice," Congressman Clay said at a news conference on Tuesday.
Moss' older brother Walter is also supporting the new investigation, according to the Associated Press news agency.
He said it was a shame that the Moss and Griffin families were still searching for the truth.
However, the former prosecutor in the case says he still believes Griffin was guilty.
"I believe the jury did the right thing, and nothing's happened that's led me to believe otherwise," Gordon Ankney told AP.
The case was re-opened after the publication of a report by Law Professor Sam Gross providing new evidence.
The report says a police officer at the scene of the crime repeatedly said that a story told by a supposed eyewitness was false.
A second victim who was wounded during the attack, Wallace Conners, was not contacted by the defence or the prosecution in the trial and did not testify, it adds.
He is quoted by the report as saying that the supposed eyewitness was not at the scene, and that Larry Griffin - whom he knew personally - did not carry out the killing.
Mr Ankney maintains that Mr Conners told the police he would not be able to identify the killer, and that Griffin was seen getting into the car by another policeman.
But Mr Gross believes the evidence is conclusive.
"There is no real doubt that we have an innocent person," he told the St Louis Post-Dispatch newspaper.
"If we could go to trial on this case, if there was a forum where we could take this to trial, we would win hands down."