Stuart Aherne was 18 when he knifed Jean Ryder, 45, in Wythenshawe, Manchester, in 2003 and was sentenced to life in prison.
The killer was found in his cell at HMP Lindholme near Doncaster, at 11.30am and staff attempted to save him but he was pronounced dead 10 minutes later.
An investigation was under way into the circumstances.
Aherne stabbed Mrs Ryder, later bragging about it to a friend, because she asked him to pick up a chip wrapper he had dropped in the street.
She had calmly told him to “pick it up” before he swore at her and told her she should clear it up.
His victim then bent down to pick up the litter and put it in the bin and Aherne stabbed her with a knife engraved with the word “Judge”.
He was arrested after he told a friend what had happened while they watched the violent 1972 movie Deliverance.
He was also found guilty of a separate wounding charge at Manchester Crown Court, relating to an attack a week before Mrs Ryder’s death.
A Prison Service spokesman said: “As with every death in custody, the prisons and probation ombudsman will conduct a full investigation.”