GARDA detectives "instigated and encouraged" an informant to kill a member of a family with close links to the south London underworld, it has been claimed at the Old Bailey in London.
Mr George Carter-Stephenson, defending alleged hitman Mr Michael Boyle (48), suggested the Garda could have halted the murder plot months before she gunned down Mr Tony Brindle in September 1995.
The barrister claimed detectives allowed the attempt to continue in order to get enough evidence to implicate a Dublin gangster, Mr George Mitchell, in the conspiracy.
During cross-examination by Mr Carter-Stephenson, garda Det Insp John Mahony vehemently denied the suggestions. He said he told Mr Boyle to distance himself from the plan to murder members of the Brindle family of south London.
Mr Boyle, of Tyrconnell Road, Inchicore, Dublin, denies attempted murder and two firearm offences. His co-defendant Mr David Roads (52), of Chaffinch Close, Croydon, Surrey, denies attempted murder, eight firearm offences, possessing an explosive substance, handling stolen goods and possessing a false instrument.
In September 1995, Mr Boyle was filmed by the South East Regional Crime Squad shooting Mr Brindle (32), before he was himself shot by the police.
The prosecution alleges the Garda discarded Mr Boyle as a "rogue informant" after he informed it of Londoner Peter Daly's plan to have "the Brindle boys" killed.
The court was told that in March 1995 Mr. Boyle told detectives about the murder plot involving Mr Mitchell and Mr Daly. While in custody in relation to another alleged extortion attempt, he told Det Insp Mahony - a sergeant at the time - he could provide the address of a "safe house" used in connection with the murder plot.
The jury has heard that at a safe house in Monkton Street, Lambeth, guns and explosives were found.
Det Insp Mahony said Mr Boyle was released but never rang with any details about the safe house. He passed Mr Boyle's information about the murder plot to the London Special Branch.
The trial continues on Monday.