Cold-blooded killers Kaniel Martin and Avie Howell showed no signs of remorse throughout their two-month trial.
They blasted newlyweds Ben and Catherine Mullany with a stolen handgun at close range in their hotel room at 5am.
As the couple lay dying on the floor, they stole two inexpensive mobile phones, a cheap digital camera and a small amount of money before making their escape.
Two weeks later, the pair - nicknamed "Sample Dan" and "Demon" - would carry out an identical attack on local woman Woneta Anderson.
After breaking into her shop, they shot the 43-year-old at close range. After stepping over her bloodied body, they ran off taking two mobile phones and a handful of top-up cards.
Metropolitan Police Detective Superintendent Keith Niven led the British team called on by the Antiguan authorities to aid with the investigation.
He said he was convinced Martin and Howell's main aim had been to kill first - and robbery was a secondary intention.
"This has been a long, complex and challenging trial," he said.
"Avie Howell was 17 years of age and Kaniel Martin was 20 when they committed these heinous crimes.
"Such is a disproportionate level of violence when balanced against the low value of property stolen, that leaves me to believe that the murders were the primary objective and the theft was a secondary intention.
"I had hoped that this trial would have established the reasons why such levels of violence were inflicted.
"They both chose not to provide an account of their actions.
"Neither defendant has showed any signs of remorse throughout the investigation or throughout this trial - even though the families of their victims have been present."
Mr Niven said justice was able to be served thanks to a joint effort by British police and forensic experts, officers in Antigua and the witnesses who testified at the trial.
"I would like to express my thanks to the high court and to the jury for bringing this matter to a final conclusion," he added
"As highlighted throughout this trial, Ben was a former police officer and member of the British Army. He had served his community and his country.
"At the time of his murder he was training to be a physiotherapist intending again to provide a valuable service to the community.
"Catherine was an eminent doctor, who had excelled in numerous specialised areas within the medical profession.
"Upon her return home to Wales she intended to continue her support to her local community as a GP.
"Ben and Cath were two hard working, talented and thoroughly decent individuals - who had everything to live for and so much more to give."
He said yesterday was the third anniversary of the couple's murder.
"This is a very difficult time for the family and our thoughts and prayers are with them, " Mr Niven added.
"Their courage and dignity throughout this investigation and this trial has been an inspiration to us all. "