Firearms found hidden in the vehicle of an accused gang member. British authorities say one of the guns seized was scrubbed clean but still contained traces of DNA from the blood of a tortured victim. (Photo: Courtesy of Police Scotland)

A pioneering forensic technique, developed in Scotland, helped bring one of Britain's most sophisticated crime gangs to justice.

Nine men will be sentenced next month for importing drugs and trafficking firearms on an industrial scale.

The group had an annual turnover of more than £100m and had links across Britain and Europe.

And they went to elaborate lengths, including using anti-surveillance equipment, to evade detection.

Members even travelled to Brazil and met drug cartels to arrange high-purity cocaine shipments to the UK, via West Africa.

Now BBC Scotland can reveal exactly how the DNA of a drug dealer was recovered from a gun used to torture him.

The High Court in Glasgow heard Robert Allan was kidnapped by David Sell and two armed men in March 2015 after fleeing Scotland for Barnsley.

Allan, who had failed to pay a £30,000 debt, was driven to a desolate industrial unit in Fauldhouse, Midlothian.

Scrubbed clean

There he was lashed with a thick chain, struck with a metal bar and left with a broken leg after being beaten with a 14lb sledgehammer.

During his captivity he was also pistol-whipped with a Beretta 9000, fitted with a silencer.

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