PC Keith Blakelock was stabbed 43 times, the court heard
A man has been cleared of killing police officer Keith Blakelock during riots in north London in 1985.
Nicholas Jacobs, 45, denied murdering the officer, who was stabbed 43 times at Broadwater Farm in Tottenham.
The Old Bailey jury heard from three witnesses who said they saw Mr Jacobs take part, but his defence team questioned their credibility.
On Wednesday, after four hours of deliberations, Mr Jacobs was found not guilty of murder and manslaughter.
Mr Jacobs - who was 16 at the time of the riot - stood up, held his head in his hands and punched the air as the verdicts were delivered. He then sat down and sobbed before being taken from the dock.
PC Blakelock's family looked distraught. One of his three sons held his head in his hands, while his widow, Elizabeth, left the court soon after the verdicts were returned.
Nicholas Jacobs, who was 16 at the time of the riots, chose not to defend himself in court
In a statement, they said: "We are obviously extremely sad and disappointed at the verdict. We viewed this trial as an opportunity to see some form of justice served for Keith.
"We hope that more people are able to come forward so that some of those guilty can be brought to justice in the future."
Defence lawyer Courtenay Griffiths QC said outside the courtroom: "I'm delighted, I think the jury reached exactly the right verdicts."
Metropolitan Police Assistant Commissioner Mark Rowley said: "Sadly, Keith's widow, family and friends still have not seen anyone brought to justice for his murder.
"The dignity, extraordinary patience and courage they have shown in their nearly 30-year quest for justice is humbling.
"We will not give up on bringing Keith's killers to justice."
Crown Prosecution Service London prosecutor Jenny Hopkins said: "It was right that all the evidence in this case was put before a jury and we respect its decision."
Retired policeman Richard Coombes, 63, who survived the Broadwater Farm attack, said: "The jury has reached its decision and we must all respect that."
PC Blakelock, 40, was repeatedly stabbed, and attempts made to decapitate him, as he tried to protect firefighters tackling a blaze at the height of the unrest on the Broadwater Farm estate on 6 October 1985.
During the trial, the jury heard Mr Jacobs had allegedly written a poem, while serving time in a juvenile detention centre, in which he boasted about "chopping" at the officer.
But his defence team claimed his account of the wounds the officer received did not match the post-mortem examination.
Mr Jacobs' prosecution followed an previous trial in 1987, when three men were convicted of the murder, before being freed four years later on appeal.
During the course of three separate investigations, a decision was made to give immunity to so-called "kickers" - those who were involved in the attack but did not use weapons - in exchange for their co-operation.
Among them were the prosecution witnesses given the pseudonyms Rhodes Levin and John Brown who both admitted kicking PC Blakelock and were given amnesty from prosecution.
About 500 police battled with rampaging youths during the 1985 Broadwater Farm riots
Some of the witnesses also received payments from police for their co-operation, the court was told.
The judge said Mr Jacobs had been within his rights not to give evidence during his trial and the jury could draw their own conclusions about his decision not to take the witness stand.
Winston Silcott, one of the so-called Tottenham Three convicted of the murder of PC Blakelock in 1987, said outside the Old Bailey: "The police are bitter about what happened, that's why they brought this case.
"My conclusion is that they had promised the Blakelock family that they would get justice for him and so they were trying to get anyone they could.
"Vengeance, that's what the police were out to get. I just hope Nicky Jacobs will be able to rebuild his life after this."