Two men convicted of murder in 1980 have been cleared on appeal.
The judges said the evidence against Terry Pinfold, from Hornchurch, Essex, and Harry Mackenney, from Dagenham, Essex, was "so unreliable that it is worthless".
The businessmen were jailed for life 23 years ago after being implicated in a string of murders by a former employee, Bruce Childs, who had confessed to a series of contract killings.
On Monday, the Court of Appeal in London quashed as "unsafe" the convictions of businessmen Mr Pinfold and Mr Mackenney.
'Not capable of belief'
Lord Woolf, the Lord Chief Justice, said fresh evidence showed that Childs - regarded as an unsatisfactory witness even at the trial - was a "pathological liar".
The judge, sitting with Mr Justice Aikens and Mr Justice Davis, said they were "unable to say where the truth lies as to these terrible murders".
But the evidence of Childs, although corroborated to some extent, was "not capable of belief".
The ruling had been predicted when the pair, both now 70, were released on bail following the hearing of their appeals in October.
In the 1970s, ex-prisoners Mr Pinfold and Mr Mackenney were in business together
making underwater diving equipment.
Convicted of four murders
One weekend in November 1974, another former inmate, toy maker Terry Eve, who shared their factory space in Dagenham, disappeared.
It was not until four years later that Childs implicated his former employers in his crimes.
As a result, Mr Mackenney was convicted of four murders, including those of haulage contractor George Brett and his 10-year-old son, Terry.
He was acquitted of murdering Terry Eve because of lack of corroboration, but Mr Pinfold was convicted of murdering Mr Eve on the basis that he procured Mr Mackenney and Childs to kill him.
Mr Mackenney was given a "whole life" tariff and faced the prospect of never being released from prison.
Childs still in prison
Mr Pinfold was first bailed, pending appeal, in September 2001 having served almost all of his recommended minimum sentence.
The pair's initial appeals had failed, but many years later the case was referred back to the Court of Appeal by the Criminal Cases Review Commission, which investigates possible miscarriages of justice.
Childs is still serving a life sentence for six murders.
None of the bodies has ever been found.
Childs claimed he had dismembered them and burned them on his domestic grate.