The British Isis killer known as "Jihadi John" may have a body double, according to a new video analysis, which also suggests that American aid worker Peter Abdul-Rahman Kassig was beaten before his death.
Analysts who have conducted close-up examinations of the footage of Kassig's severed head say the hostage's face shows a large bruise above his left eye, suggesting he put up a struggle.
Freeze-frame analysis also appears to show that while there only appear to be 18 or 19 jihadists and victims in the main part of the video, there are in fact 22. In addition to the execution of Kassig, the film also shows a mass execution of Syrian regime officers and pilots.
As well as "Jihadi John", who plays the central role, one other is wearing a balaclava, a fact that seems to be deliberately hidden as it is visible only from a single "screen grab".
That has led the analysts to speculate that he might be intended to be a double for the chief executioner, perhaps to confuse drone surveillance. There seemed little reason to have another masked man on hand, given the fact that all the other men present show their faces except for Jihadi John.
"It could be a body double or a decoy," said Veryan Khan, the editorial director with the Terrorism Research and Analysis Consortium (Trac), which looked at the video for Quilliam, the British anti-extremist think-tank.
"I'm not trying to say I know the answer, but his shape and size are very similar."
The analysts believe parts may have been shot and reshot several times, and that it might have taken between four and six hours to film.
Although each jihadist seems to have an individual hostage to kill, careful study shows it is not always the same one. Hostages are exchanged.
The final section, with Kassig, is claimed to be filmed in Dabiq. Although the background is clearly Dabiq, Trac says it believes Jihadi John and the head were filmed elsewhere, and superimposed in editing.
Winter said it was possible the jihadists left out Kassig's body because "he struggled and his video became unusable for marketing purposes".
The analysts believe the editing is so sophisticated the full film may have been sent abroad to a professional studio.