Each of Quyen Ngoc Nguyen's twisted killers previously murdered a pensioner in the 1990s before they met in prison while serving life sentences.
Maintenance man Stephen Unwin, 40, had a history of setting fires at the scenes of his crimes, while William McFall preyed on a defenceless elderly woman.
Unwin admitted murdering 73-year-old John Greenwell in Houghton-le-Spring, Tyne and Wear, on Christmas Day in 1998 by attacking him in bed with a camera and then stabbing him.
Unwin stole the pensioner's TV and video recorder and then started three fires in the property, so his victim had to be identified by his dental records.
In 1991, Unwin set light to an HGV he had broken into, and in 1995 he started five fires in the property of another elderly burglary victim who was rescued by neighbours.
Unwin was jailed for life for murder at Newcastle Crown Court in October 1999 and was released on licence in December 2012.
William McFall, originally from Northern Ireland, murdered 86-year-old Martha Gilmore with a hammer during a break-in at her home in Greenisland, Carrickfergus, in May 1996.
His victim had mobility problems and, when she disturbed the burglar, McFall knocked her to the ground before hitting her with the weapon.
He would later tell a probation officer he killed Mrs Gilmore "due to alcohol, stress and panic" when he realised she had seen him.
He admitted murder, was jailed for life in April 1997 at Belfast Crown Court and released on licence in October 2010.
McFall had previous convictions for violence and firearms offences.
The painter and decorator was living in Blackpool but teamed up with Unwin for work and stayed with him in the North East for spells.
Video clips found on a mobile phone after their arrest show McFall posing with a gun at a party while Pink Floyd's Wish You Were Here played in the background.
In another, filmed as they ate at a pub, Unwin talks about hiring a "brass" - a prostitute - for both of them at a cost of £100, causing McFall to laugh maniacally.
In two more clips, the pair show off while filming a cannabis farm.
The maintenance men worked for landlords on cheap properties, sometimes repairing them after they had been used to grow cannabis.
The pair, using their notoriety as convicted murderers, would "tax" some of the growers by stealing their crop.
McFall even posed for a grinning selfie in Unwin's car after they had disposed of Quyen Ngoc Nguyen's body, and he sent the snap to his girlfriend in Blackpool.