A teenager strangled his 91-year-old grandfather and stole his £300 pension from under his pillow.
Stephen Lang was jailed for life after he admitted murdering his granddad Thomas after the pensioner disturbed him as he tried to steal his pension.
A jury at Truro Crown Court heard that last April, Lang - who is now 20 - had grabbed his grandfather by the throat, lifted him out of a chair and shoved him to the floor at his sheltered accommodation before grabbing the pensioner's wallet hidden under a pillow.
Stephen had no reason to kill his grandfather, who would have gladly given him money had he asked for it, but he wanted the money to feed his £140-a-day drug habit.
Despite his injuries, Mr Lang was able to summon help to his home in Launceston, Cornwall.
He told police and his son what had happened, but died from his injuries three days later in hospital.
In a statement, Mr Lang's family said: "The fact that he was killed by his grandson, who had a good relationship with Tom, has devastated us as a family.
"Stephen had no reason to kill his grandfather, who would have gladly given him money had he asked for it."
Detective Inspector Stuart Ellis, who led the murder investigation, said: "I cannot begin to understand Stephen Lang's motivation for this crime, but the fact that he could inflict these injuries on his own grandfather is truly shocking."