Sandeep Patel suffocated 97-year-old Annie Temple at her home in Kinglassie, Fife on October 25 in 2019.
The chronic gambler had earlier preyed on Annie for her money.
The 38 year-old medical researcher was convicted in June of murder following a protracted trial.
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On Monday he was handed a life sentence at the High Court in Glasgow.
Judge Michael O'Grady QC said he had not detected "a flicker of remorse, regret or hint of humanity" from Patel.
He said: "The least Annie Temple could have expected was a dignified and peaceful passing.
"But, you robbed her of that. In its place, you inflicted on her a death filled with confusion, pain and terror.
"Those who practice in these courts see and hear the dreadful things human beings do to one another.
"Sometimes crimes have the power to profoundly shock - I have to say yours is one of them.
"To kill a 97-year-old woman who had embraced you as a friend in such fashion, in her own home and bed and with such cruelty is wicked beyond any description."
Patel, who appeared via video link from prison, showed no emotion as he was sentenced.
Patel was a ‘problem gambler’
Former insurance worker Annie, known as Nan, lived alone at her home in Kinglassie.
She was known to have only a couple of regular visitors, which included Patel's mother.
Jurors heard how the pensioner was found dead in her bed.
Police initially did not treat the death as suspicious.
Patel was quizzed by a constable and lied he had not seen Annie the day she died.
Patel said Annie had been a patient of his father's and that he had known her "ever since I can recall.”
He claimed he carried out odd jobs for the OAP including bringing bananas to her.
He said: "The last time was a week Tuesday past. There was an issue with the pressure in her boiler."
Annie's friend Wendy Bradbury told the trial how she also spoke with Patel and he appeared "perfectly normal" when discussing the pensioner's death.
But prosecutors said Annie had been killed with blunt force trauma inflicted on her head and body.
She was also said to have had her airways "obstructed and constricted" by means unknown.
Patel, who lived with his mother in Cardenden, Fife, was charged with murder on November 15, 2019.
Annie's friend Wendy told how the OAP "did not trust" Patel.
The witness said: "She had money gone missing from her sideboard.
"She believed the money had been taken by Mr Patel."
The murder and fraud probe revealed Patel was a self confessed 'problem gambler'.
He had bet over £109,000 between 2016 and 2020 winning just around a quarter of that back.
In desperate need for cash, he used Annie while claiming to be a helpful friend.
Patel cashed a number of cheques - totalling £1,500 - in Annie's name the week prior to her death.
He had then tried to pocket a further £1,250 two days before the murder - but suspicious staff at Annie's bank blocked the payment.
Annie was spoken to and admitted she did not even know she had a cheque book.
It also emerged that in June 2019, Patel had gone with Annie to her bank hoping to transfer more than £4,000 for a supposed car purchase.
Staff again did not allow the transaction to go through.
Patel once got a £5 cheque as an overpayment from a car company - he then tried to cash it for £500 by illegally adding two zeroes.
Police examined a number of Patel's electronic devices including messages on them.
In one WhatsApp text in January 2019, Patel stated to a friend: "Mrs T got 2-300k in bank".
He also discussed the house being worth "100k".
Other messages in the month of the murder revealed Patel being warned about arrears in loan payments.
He had earlier asked for a £250 increase.
CCTV evidence also pinned Patel being near to Annie's home on the morning of the killing.
The trial in June was hit by several delays mostly sparked by Patel, who appeared in the dock in crutches.
His claims included fears he had covid, that he could not concentrate on evidence due to "ringing" in his ears and also stated he had not taken medication prior to leaving prison, where he was on remand.
Solicitor advocate Iain Paterson withdrew from defending him to be replaced by QC Mark Stewart.
A total of four new juries were picked before a trial was finally completed.
David Green, Procurator Fiscal for Homicide and Major Crime, said: “Sandeep Patel took advantage of the trust fostered by his family’s relationship with Annie Temple and used it to defraud her of her money. When Ms Temple then discovered his betrayal, he brutally murdered her.
“It’s thanks to painstaking work by detectives and prosecutors that Patel has been brought to justice.
“Our thoughts are with Annie Temple’s loved ones as they attempt to come to terms with her murder.”