New forensic analysis of photos of scene of the White House Farm murders which were given to The Guardian have cast even more doubt on the case against Jeremy Bamber, who has so far served 41 years for the brutal crime.

Jeremy Bamber handed photos of the crime scene to The Guardian late last year, which they have since had analysed by leading forensic biologist Sue Carney-Gannon. Using bloodstain analysis, Carney-Gannon has pieced together what happened in 1985, combining ‘biology, chemistry, physics and maths to examine the size, shape and location of blood left at a crime scene’. According to the newspaper these photos have never been analysed in this way before.

This new analysis suggests that Bamber’s sister, Sheila Caffell, was the perpetrator, with evidence suggesting she shot her adoptive parents and her twin boys before turning the gun on herself. At trial it was argued that this couldn’t have been the case because of the nature of her injuries and the fact that a silencer was used on the gun – rendering it impossible that she would have been able to shoot herself. This bloodstain analysis challenges that theory. Previous forensic intervention has suggested it is possible that Sheila shot herself once non-fatally before pulling the trigger a second time, and Carney-Gannon’s new findings support a forensic investigation the Guardian commissioned from the forensic physician Professor Jason Payne-James into whether or not a silencer was used.

Jeremy Bamber, who is now 65, was convicted in 1986 at Essex Crown Court. He has always denied committing the offences.

Sheila Caffell was receiving medicating for a schizoaffective disorder at the time of the murders, and had reported hallucinations. The circumstances of the police investigation also remain highly controversial – the crime scene was not secured for 32 days, and in the hours and days immediately after the murders over 40 police officers entered the house, destroyed clothes and bedding, and even moved bodies and the murder weapon. The silencer that was critical to the case against Bamber was found three days after the crime by relatives who entered the house, and who stood to benefit from inheritance from the deceased if Bamber was out of the picture.

These new findings will be passed to the Criminal Cases Review Commission, the only body with the power to refer the case back to the Court of Appeal. The CCRC has previously spent four years analysing the potential the case was a miscarriage of justice before rejecting it for referral.

Now that much of the prosecution case has been dismantled, The Guardian says ‘it is hard to see how the commission will not be swayed by Carney-Gannon’s findings’.

Bamber’s solicitor, Mark Newby, wrote in response to the investigation: ‘Yet another independent report raising serious questions over the conviction and its safety, great work by the Guardian showing the importance of investigative journalism’.

Bamber has this year launched a legal challenge against a decision to ban him from speaking to the press, and almost everyone else, from his prison. The challenge against the governor of Wakefield prison and the Ministry of Justice comes following restrictions which came in into place after investigations by the Guardian’s Simon Hattenstone and Heidi Blake writing for the New Yorker.