Julie Kenyon's legal team said she had a personality disorder in 2001
A West Yorkshire woman who was secretly taped confessing to smothering her grandmother has lost an appeal against her murder conviction.
Julie Kenyon was recorded by her sister in 2001 as she admitted killing 89-year-old Irene Waters five years after her death at their Halifax home.
Her case went to appeal on the basis that she was suffering from a personality disorder in 2001.
Kenyon was jailed for life in 2003 at the age of 46.
Judges had been urged to rule Kenyon's conviction unsafe but her appeal was dismissed on Tuesday by Lord Justice Hughes, Mr Justice MacKay and Mr Justice Lloyd Jones at the Court of Appeal in London.
Lawyers for Kenyon based their case on the testimony of two experts relating to her psychological profile and the likelihood of her making false confessions.
In the ruling, Lord Justice Hughes said they found this evidence would not have assisted Kenyon, nor been in her best interests in contesting the murder charge.
He added: "The evidence now proffered would not be likely to afford grounds for quashing the conviction.
"Accordingly, we decline to admit it and the appeal must be dismissed."
The judges earlier heard Kenyon's conviction had been based on three confessions made to her mother, sister and a family friend in 2001.
These came after an inquest at the time of Mrs Waters' death in 1996 which found that she had died of natural causes.
Kenyon did not appeal when she was convicted at Newcastle Crown Court but applied to the Criminal Cases Review Commission (CCRC) in October 2003.
The CRCC decided to refer her conviction to the Court of Appeal "in light of new expert psychological and psychiatric evidence gathered by the commission which raises the real possibility that the court may quash the murder conviction on appeal".
In a tape recording made by her sister, Kenyon, of Dodge Holme Court, Halifax, confessed to smothering her grandmother with a pillow because she had asked her to help her to die.