But last month Diamond was granted the chance to appeal his conviction by the Criminal Cases Review Commission, on grounds of diminished mental responsibility.
And for Christopher's grieving family, it has made their suffering even worse.
Speaking on behalf of his parents, Jean and Philip, who remain too devastated to talk about what has happened, Christopher's aunt June Hunt said: "This is always a very bad time for the family.
"Christmas is not a time of celebrating for them. It is when they do their mourning.
"Jean went to Burnley cemetery to lay a wreath on his grave on Christmas Day.
It never gets any easier.
"One of the worst things is that his head was never found and Diamond has never said where it is, so Chris had to be buried without it.
"But Jean says that she thinks of him as all mended up in heaven.
"But the fact that they've got the added upset of the possible appeal has made it even harder this year."
Philip and Jean, both 53, will be notified by police when Diamond appears in court to lodge his appeal, and they are already looking into a possible private prosecution.
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