The Fishers were victims of a planned attack, police believe

Graham and Carol Fisher, aged 60 and 53, were beaten after they had been shot at their bungalow and petrol station on the A39 near Wadebridge on 5 November.

Uniformed officers stopped motorists who were using a section of the A39 close to the garage to gather information.

Police believe the Fishers were victims of a planned and personal attack.

Psychological profile

"What we are doing is stopping vehicles that are coming past the premises," said Detective Sergeant Steve Hatton.

"We are asking them three very basic questions.

"If it's 'yes' to any of those questions they speak to a CID officer who takes very brief details with a view to seeing them at a later, more convenient, date."

Officers involved in the Fishers' death are also asking the National Crime Faculty to provide a crime profiler to build up a psychological profile of the killer.