A DETECTIVE who investigated some of the region's most notorious crimes is to retire after 34 years with the same police force.

For six years until 2006, Detective Superintendent Harry Stephenson was one of Durham Police's senior investigators, leading inquiries into about 30 murder cases.

Yesterday, the 53-year-old said: "I'm leaving this organisation very happy. It's been the best 34 years of my life. I wouldn't swap it for anything."

Among the high-profile cases Det Supt Stephenson handled was the murder of Julie Smailes, a 27-year-old sales manager found dead in her home in Leadgate, County Durham, in October 1996. His team's work identified John Thompson, who hanged himself in August 1998, as being at the scene.

Det Supt Stephenson said he was "fairly confident" Thompson would have been convicted, but believes another person was involved.

He said: "There is still a fear in the Derwentside area. I still believe there are people who know what happened.

"For whatever reason they won't come forward. That's a little bit frustrating."

Police are awaiting the results of forensic tests conducted in April.

Det Supt Stephenson also led the investigation into the activities of Dr Howard Martin, who, in December 2005, was cleared of murdering three patients with morphine overdoses.

He said: "I was disappointed, but felt really sorry for the families, because they had stood up and given evidence.

"Those three families had remarkable courage."

Born in Gateshead, Harry Stephenson joined Durham Police as a constable based in Stanley.

He later worked in Chesterle- Street, Newton Aycliffe, Consett, Durham and Darlington.

He was responsible for an undercover drug operation in Darlington; and another in Grange Village, near Chesterle- Street, which won him a standing ovation at a public meeting in the village.

Since 2006, he has been head of Durham Police's professional standards unit.

Married with two grown-up children, he is planning to spend his retirement doing consultancy or charity work.

He retires in August but his last day at work is Friday.

He said: "My proudest achievement was being able to reach some conclusions and results for the families of people that have been murdered.

"It's been a fantastic career.

I'm proud of having had some contribution to the lives of people in Durham County."