An independent forensic expert was today arriving at the Deepcut Army barracks to begin detailed examinations of the sites where four soldiers died in mysterious circumstances.

Frank Swann will lead a small team over the next four weeks in a forensic probe of the base.

After setting up a mobile laboratory at the camp, he hopes to spend 20 days, examining each of the four sites in turn.

His work is part of an independent investigation by the families, which is running alongside a police inquiry into the four deaths.

Private Geoff Gray, 17, from Hackney, east London; Private Sean Benton, 20, from Hastings, East Sussex; Private James Collinson, 17, from Perth, and Private Cheryl James, from Llangollen, north Wales, died from gunshot wounds at the barracks between 1995 and 2002.

The families have refused to accept the theory that all four soldiers committed suicide using their own rifles and have accused the Army of a cover-up.

Mr Swann, a forensics and ballistics expert, said: ''We will be using laser and detection equipment at the scenes of each of the deaths.

''We will also be reconstructing and re-enacting the incidents from the original crime scene photographs.

''From these methods we should get a good idea of what took place, and using standard ballistics methods whether the individuals shot themselves or not.''

In an initial report last month, Mr Swann said wounds suffered by Pte Benton and Pte Gray could not have been self-inflicted.

He was also 70% sure the fatal wound to Pte Collinson was not self-inflicted, but more tests were necessary in the case of Pte James.

His team will test SA-80 rifles supplied by the Army, using live rounds at a firing range.

Examination of the weapons belonging to the soldiers would take place at a later date.

Mr Swann was given permission to enter the Surrey barracks by defence minister Adam Ingram.

Jim Collinson, father of James, who died last March, welcomed the next stage of the independent forensic investigation.

He said: ''The start of tests at the barracks is a big step forward for all the families. This is what we have been waiting for for so long.''