Mathew Hardman, then 17, from Anglesey, north Wales, was last year jailed for a minimum of 12 years following his trial at Mold Crown Court.
The jury was told the art student killed 90-year-old Mabel Leyshon and removed her heart in a Satanic-style ritual in November 2001.
His first bid to appeal was rejected by a single judge at the Court of Appeal earlier this year.
A new application for leave to appeal was rejected today by three judges, Lord Justice Mantell, Mr Justice Butterfield and Mrs Justice Cox.
Hardman, now 18, has always denied harming the pensioner.
The three judges rejected a submission that the trial judge wrongly allowed potentially “devastating” evidence to go before the jury.
Hardman’s mother Julie left the court in tears and did not comment on the outcome of the hearing.