What went wrong in the French Alps murder investigation – by the detective who saw it all

telegraph.co.uk:

staggeringly violent case of the al-Hilli family, three of whom were, along with a French cyclist, shot dead in an Alpine beauty spot on 5 September 2012.A decade on, Preston, who led the British end of the investigation for three years, can still see the crime-scene photos of Saad al-Hilli, his wife Iqbal and her mother Suhaila al-Allaf, each shot twice in the head, in the family’s bullet-riddled BMW.

He thinks about the two little daughters who somehow survived the attack, and wonders what their lives are like today. He goes over and over the facts involuntarily, wondering what he could have done differently and what he might have missed. ‘It leaves an emotional footprint,’ he says.Having worked on dozens of murders, the al-Hilli case is the retired detective chief inspector’s major unfinished business.

It is also the ‘most complex and challenging’ investigation of his career – but it should not have been unsolvable. Preston believes the murder inquiry was hampered by a series of blunders by French investigators, who apparently failed to secure vital pieces of evidence and, in his view, spent years going down blind alleys.

He claims that instead of keeping an open mind about who might have pulled the trigger, and why, they fixated on a single theory, eventually abandoned, meaning the trail had gone cold by the time they considered alternatives.‘I couldn’t get the investigation in France to change direction and that I bitterly regret,’ he says. ‘There were times when the French asked us to do things and we took them at face value because we were fearful of damaging the relationship, when we should have just said, “You’re wrong.”’This is all laid out in a new three-part Channel 4 documentary, Murder in the Alps.