Police are turning to the criminal fraternity for help in tracing the hit-and-run driver who killed 87-year-old great-grandmother Betty Cooper.

Despite appeals for information from back street garages and the public, detectives have yet to find the Ascot Green BMW convertible that hit the mother-of-12.

They have now turned their attention to criminals on Teesside who might know the car and driver's whereabouts.

The officer leading the inquiry has also given his personal mobile number to encourage people to ring with information.

Acting Detective Inspector Paul Beddows said police believe the car has been hidden in a lock-up garage or back street workshop.

He said: "There has been widespread publicity surrounding this case and the driver will not be able to use a reputable firm for the work needed.

"We are asking criminals who know what has happened to look to their conscience and think of the trauma being suffered by Mrs Cooper's family.

"Would they like that to happen to their friends or relatives? All it needs is one call, anonymously if they like, to solve this. That one call could at least give the Cooper family some peace of mind.

"This death will also be playing heavily on the driver's conscience and it would be far better for him to come forward now."

Anyone with information to help trace the driver and car is asked to call Acting Det Insp Beddows' confidential hotline on 07736 627582. Alternatively they can ring Stockton police on (01642) 302234 or Crime-stoppers anonymously on 0800 555111.