It was a huge police effort to convict the three - with more than a thousand statements taken and more than three hundred vehicles traced which had passed the layby on the A358 where Catherine's body was found.
Forensic investigations played a key part in their conviction.
Ian Axton reports:
The family of Catherine Wells-Burr has written to the Prime Minister after hearing her killers could end up serving a shorter sentence.
The parents of Catherine Wells-Burr have described how they comforted her alleged killer - as her burned corpse lay in a nearby field.