London, June 21 : Dozens of convicted killers and gangsters in UK could walk free after a landmark House of Lords ruling which challenges the use of anonymous witnesses in trials.
Lawyers are expected to launch appeals against a series of convictions involving some of Britain's most ruthless gangland killers.
Assistant Commissioner of the Metropolitan Police, John Yates, described the law as a cause for grave concern. The decision by the House of Lords means defendants in criminal trials will have a legal right to know the identity of the witnesses testifying anonymously against them, he added.
It threatens future trials and could lead to a series of appeals by individuals, who have been convicted by evidence given anonymously in court, The Telegraph quoted Yates, as saying.
The ruling, earlier this week, quashed a double murder conviction secured after witnesses who feared for their lives gave evidence anonymously. The law lords ruled that defendants had a right to confront their accusers and cross-examine them.
Police now believe that up to 40 individuals in London alone convicted of murder or other serious crimes could appeal and walk free if the witnesses refuse to reveal their identity in a retrial.
Dozens more previous cases will be affected nationwide and at least three trials currently being heard in England are on the verge of collapse over the legal argument.
"This is potentially disastrous. A lot of good work is being undone, and this will play out so badly in terms of those we are trying to reach out to communities. It almost feels like we have broken our word," Yates said.
"To see clearly guilty people walking free would be just awful," he said.
"Special measures are only used in the most extreme cases, which means these are our most dangerous criminals, people who have been jailed for up to 40 years. And they could be walking free," Yates said.
Police have identified an initial list of 16 men who may appeal because of the ruling. The ruling could also affect terrorist trials and cases where undercover police or MI5 officers have given evidence.