Matthew Hamlen, 37, stabbed 77-year-old Georgina Edmonds 37 times and then bludgeoned her to death with a marble rolling pin at her home in Brambridge, Hampshire.
He was convicted after an eight-year investigation thanks to DNA evidence.
Mrs Edmonds”s son Harry – who found his mum in a pool of blood – called for the death penalty to be reinstated for “loathsome individuals who commit crimes of this magnitude”.
Speaking outside the court, Mr Edmonds, 60, said: “Operation Columbian has been one of the most complex criminal investigations ever mounted in Hampshire.
“It has contained almost as many twists and turns as an Agatha Christie thriller.
“The investigation has lasted eight long years and, sadly, was not a tale written to entertain people but the true story of a wicked and vicious crime – the torture and murder of a frail and elderly lady in the sanctity of her home – and of the dedicated men and women of Hampshire Constabulary who pursued this devious and vicious murderer and, thank God, finally brought him to justice.”
He added: “I should remind you Matthew Hamlen stabbed my mother 37 times and then beat her to death with a marble rolling pin.
“The death penalty is no longer a sentencing option for judges in this country and in my view it is a matter of great regret that we can no longer execute the loathsome individuals who commit crimes of this magnitude.”
The son of the last person to be hanged in the UK – Peter Allen – has called for the death penalty to be reinstated for ISIS terrorists.