Elsie Frost, 14, was stabbed in the back and head as she walked through a railway tunnel just off a canal towpath in Wakefield in October 1965.
Detectives had expected to charge Peter Pickering, also known as the Beast of Wombwell, after renewed appeals yielded fresh leads.
But the 80-year-old child killer and sex offender died in March in a secure psychiatric unit after more than 45 years behind bars.
Colin Frost, Elsie’s brother, said the family were working with police and Wakefield MP Mary Creagh to see if there was a way to have the inquest into Elsie’s death reopened.
“What we’re wanting to do is get the truth out so everyone is fully aware of Pickering’s crimes,” he said. “We do still have the feeling of being cheated out of justice but what we do see is he probably wasn’t up to standing the rigours of a murder trial.”
He said he believed they might be setting new ground if the inquest was reopened and it could help other families in historic murder cases.
“We’ve still got hope,” he said. “Hope of getting the story out there, for everybody to understand the crimes of Peter Pickering and then we might be able to link him to Elsie’s murder in the correct way. In short, we’re continuing the fight.”
Pickering was jailed for life for the murder of 14-year-old Shirley Boldy in 1972.
Shortly before his death, he had been convicted of the knifepoint rape of an 18-year-old woman in the Barnsley area in the weeks before Shirley’s murder.