tey didn't rule out a sexul motive as her clothes were disturbed. thats all there is on the motive though.police think there is a high chance the same killer murdered someone else as well.
"Bushell, was found with her throat cut 300 yards (270 metres) from her home. Bryant was stabbed a number of times, her killer had apparently returned to the scene four months later to place her missing glasses back at the site. The apparently motiveless killings, as well as their particularly brutal nature and apparent links, led to fears that a
serial killer was at large in the south-west at the time."
Lead detective Chris Boarland concluded: "This was a planned murder. It was not about Lynda Bryant. This is somebody who was looking for somebody in an isolated location." both the Bushell and Bryant cases it was ultimately concluded that the motive was sexual, even though neither of the victims had been sexually assaulted." In both cases this was because of the way their clothes had been disturbed by her killer.
en.wikipedia.org