Terence Michael Whall thought he had committed the perfect murder, when he shot and killed Gerald Corrigan on Good Friday of ast year.
There was no forensic evidence, no direct eye witness to the shooting and no one saw him going to and from the scene of Mr Corrigan's house at Gof Du near Holyhead.
Any evidence was circumstantial and Whall thought he was going to get away with it.
But lead investigator Det Chief Inspector Brian Kearney said the case against him began to build when the public, businesses and experts joined forces to provide vital parts of the jigsaw.
Piece by piece the evidence came in linking Whall to the terrible crime.
By the time it came to trial, the investigators were able to show how Whall had ordered various crossbow bolts and broadheads from early March in preparation for the murder, how he'd practised on a punchbag at his home.
Telematics from the "murder vehicle" Land Rover Discovery he conspired to burn on June 3, thinking he'd destroy the evidence, was actually stored by Jaguar Land Rover and showed he 'd driven to Gof Du and "scoped it out on April 17.
The data also showed how he hid the vehicle the following night near Porthdafarch Beach and in the dead of night walked along the coastal path, interfered with Mr Corrigan's satellite dish, drawing the pensioner out before shooting him in "cold blood" as he lay in wait, with a high powered crossbow.
Karen Dixon of the Crown Prosecution Service said: “The case was really unusual in that there was no suspect at the start, only one piece of evidence to follow.
“We had to use the various fragments of evidence to build a picture for the jury, demonstrating how they were connected.
“The telematics evidence from the Land Rover was key in showing that Terrence Whall was not only at the location at the time, but that he’d visited the night before, checking the area.
“Even though the car was burnt out, it did not prevent us from obtaining and using this important data, which even told us how long the boot was open when the killer took the crossbow out."
She said Whall had planned what he was going to do and carried out a 'cold-blooded killing'.
“Crossbows are deadly, silent weapons that can cause horrific injuries, which in this case proved fatal", she added.
“Our thoughts are with the family and friends of the victim today, as they have been throughout the court process. We thank them for their strength and support.”
DCI Kearney said the case had been solved "by you, our community".
"We have received brilliant help from witnesses, a combination of local people, holiday makers and businesses provided us, your police service, with the evidence needed.
"In such a cold-blooded killing, I am eternally grateful to all who had the courage to come forward thereby protecting our community", he added.
