It was a scam they thought would never be detected, but the two corrupt officers convicted of selling firearms would eventually be caught - by another crime.
Maurice Allen and Damien Cobain served as firearms inquiry officers.
Their duties included carrying out checks at the homes of people who had applied for a shotgun or firearms certificate.
However, they would then casually mention they knew of a gun for sale which would be suitable for the applicant, once the certificate was granted.
They knew that they would have the complete trust of those prospective certificate holders, one of whom was builder Kevin Dowson.
He applied for a certificate after deciding to take up clay pigeon shooting.
Due for destruction
Mr Dowson told the BBC: "The police are the people who look after us, aren't they? So it was one 100% trust.
"Damien Cobain came to my house and inspected my cabinet and made sure everything was OK and then asked if I'd seen a gun I wanted.
"I said I hadn't and he said he knew someone who had one for sale when I got my certificate through.
"I had no idea he was doing something that was illegal."
But it was. The gun he sold Mr Dowson had been handed in for destruction by somebody who had inherited it following the death of a relative.
The rules on the destruction of such guns are drawn up by the Home Office, but are administered by individual police forces.
Allen, of Houghton le Spring, and Cobain, from Sunderland, simply sold the guns on.
The pair were eventually brought to justice thanks to another criminal.
In December 2008, a gun was among the items stolen by a burglar who broke into a remote farmhouse in County Durham.
When two officers went to investigate, they asked the farmer for the gun's serial number and were told: "You should have the serial number yourselves, because I bought the gun from Durham Police."
'Greedy and corrupt'
An inquiry involving officers from Durham's counter-corruption unit began and Allen was arrested, followed by Cobain.
The pair pleaded guilty to misconduct in a public office at Newcastle Crown Court in January.
They have now been sentenced to suspended jail terms.
Allen was sentenced to 51 weeks, which was suspended for two years, and Cobain to 40 weeks, suspended for 18 months.
The constabulary says the way its firearms department now operates makes it unlikely such an abuse could happen again.
Chief Constable Jon Stoddart said: "I am confident we are much tighter than we were.
"We have looked at our processes and we have got more intrusive supervision and more active supervision, and we will test that system over and over again to make sure it is robust."
Speaking about Cobain and Allen, Mr Stoddart added: "They were greedy. They were corrupt. And they have very few morals at all.
"Durham Constabulary has an excellent name, and it was sickening to think that these two could act so brazenly as criminals.
"Do I have any sympathy for them? Not at all. They are criminals and their conduct has been beneath contempt."