A man who served eight years for murder has been freed after evidence showed he had attention deficit hyperactivity disorder (ADHD) when he was tried.
Court of Appeal judges ruled Billy Joe Friend's conviction was not "safe" as he would not have been able to participate effectively in the trial.
Mr Friend, now 23, was found guilty of stabbing an 18-year-old man in Plumstead, south-east London, in 1996.
The prosecution and judges agreed a retrial was not in the public interest.
'Severe and disabling'
Quashing the conviction, Lord Justice Mance said understanding of the condition had "significantly increased" since Mr Friend's trial.
"Through no fault of the appellant, his advisers, or anyone, the nature and extent of his problems was not fully appreciated at trial as it now has been," he said.
Friend was a juvenile when he stood trial for the crime with his brother and another person.
Fresh evidence at the appeal showed that Mr Friend's ADHD was "severe and disabling".
The judge acknowledged that Mr Friend had served "a very substantial
period, particularly in light of this appellant's mental condition then and
After being released from the cells at the Royal Courts of Justice, Mr Friend said he was happy to be out.
"It's been a long time for something I didn't do and now I just want to get on with my life," he said