An independent forensics expert is starting a four-week investigation at the Deepcut Army barracks where four soldiers died in mysterious circumstances.

Frank Swann, who was hired by the soldiers' families, is already convinced two of the deaths were not suicides.

Starting on Monday, he and a small team will be examining four sites where bodies were found at the Surrey barracks for fresh evidence.

Using standard ballistics methods [we will establish] whether the individuals shot themselves or not Frank Swann

Private Geoff Gray, 17, from Seaham, County Durham, Private Sean Benton, 20, from Hastings, East Sussex, Private James Collinson, 17, from Perth in Scotland, and Private Cheryl James, from Llangollen, north Wales, died from gunshot wounds at the barracks between 1995 and 2002.

Their families do not believe the four committed suicide by turning their own rifles on themselves, as Army investigations concluded.

They have launched their own investigation, which is running alongside a separate police inquiry.

'Not suicides'

Mr Swann, a forensics and ballistics expert, said the team would be re-enacting the incidents from original crime scene photographs.

"We will be using laser and detection equipment at the scenes of each of the deaths.

"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."

The start of tests at the barracks is a big step forward for all the families Jim Collinson Father

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 later.

Mr Swann, who said he had been given just �4 by the families to act for them, 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 investigation.

All we've ever wanted was the truth Geoff Gray Father

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."

Pte Gray's father, also called Geoff, told BBC News: "All we've ever wanted was the truth.

"Maybe this investigation will find out what happened to our children."

Mr Swann said he had been advised by Surrey Police that they would consider the findings of his investigation.