Standage was on Monday convicted of the shooting murders of John Lewis Thorn in 2006 and Ronald Frederick Jarvis in 1992 after an investigation spanning three decades in all.

In his first interview since the result Detective Inspector Glenn Lathey said there was no doubt Standage, who maintains his innocence, was their man.

‘‘Stephen Standage committed both of those murders, there is no doubt whatsoever,’’ he said.

‘‘I’d describe Standage as a very cold, calculating type of criminal, and a very cowardly criminal I might add, given the nature of the murders.’’

In Hobart, Supreme Court Justice Stephen Estcourt jailed Standage for 48 years.

As the verdict was read out, Standage’s own words to undercover officers that he was too smart for police came back to haunt him.

For detectives there was no smoking gun or demonstrable slip-up by the killer, just gruelling police work over many years.

The force’s cold case unit – since disbanded – took over the investigation in 2009.

At the time the Thorn murder was being investigated by Launceston CIB.

When it became clear the same man was behind both deaths the specialised unit took the reins of the two probes.

‘‘It’s important we acknowledge the very very thorough efforts of original investigation teams ... it was invaluable in producing the outcomes that it did,’’ he said.

‘‘However, the cold case unit did have some advantages.’’

Inspector Lathey explained the unit could exploit advanced technology and forensic analysis along with covert policing techniques which had improved vastly over the years.

In a first for Tasmania, the ‘‘Canadian technique’’ (so-called for its regular use by the country’s Mounties) saw two undercover officers from Victoria befriend Standage and masquerade as underworld figures to gain his trust.

This aspect of the operation elicited ‘‘invaluable’’ information from Standage, who spoke to his new ‘‘friends’’ of where Mr Thorn was killed, how he was murdered and his theories as to why the man was slain.

‘‘It was a complex investigation it was very involved. We used every available investigative tool at our disposal,’’ he said.

‘‘On such a serious charge as murder we have to make sure all the Is are dotted and all the Ts are crossed and that takes time.’’

It’s a result he described as satisfying for all involved.

‘‘To be able to bring some closure to the families is very pleasing to the investigation team. These people have suffered and will sufferer forever,’’ he said.

‘‘It’s a very appropriate sentence, it’s another example of the judicial system in Tasmania operating correctly and effectively.’’