Peter Kassig, the American aid worker murdered by Isis (Islamic State) in Syria, may have been killed by a gunshot wound rather than beheading, analysis has suggested.
Medical experts who have studied the Isis propaganda video which shows his severed head said he may have been shot dead before being decapitated.
The analysis, carried out by a surgeon, lends weight to theories that Kassig, a former soldier, may have resisted his captors when they attempted to inflict on him the kind of ritualised beheading carried out on other hostages.
Unlike previous Isis videos, the footage released in full last month does not show the murder itself, suggesting the jihadists thought footage of a captive who fought back would be of limited propaganda value.
Detailed examination of the video also indicates that "Jihadi John", the Isis fighter with a British accent shown standing in the Syrian Desert with Kassig's bruised and bloodied head at his feet, may have been superimposed into the scene.
The research has already revealed the video was shot with the aid of a sophisticated film editing software package, which costs around $400,000.
The analysis, which is due to be published in full this week, has been conducted by Quilliam, the British anti-extremist think-tank, in conjunction with the US-based Terrorism Research and Analysis Consortium. They enlisted the help of surgeons and video experts, whose identities have been kept secret for security reasons.
Charlie Winter, a Quilliam researcher, said: "We have had a senior face and neck surgeon independently look at some of the screenshots we took. His initial assessment was that a contusion above Mr Kassig's left eye was a gunshot wound."