This week, ISIL released a video of the beheading of American journalist James Foley. The executioner in the video has already been identified as a British ISIL leader, known only as "John" or "Jihadist John." Several of his past hostages recognized him from the video, and as lead hostage negotiator for ISIL's division in Syria, conducting negotiations online with families.

Though John wears black robes and covers his face in the video, his distinct accent, eyes, height, and hands are being used as clues to identify him. For example, from the video, experts determined he is left handed.

His accent is perhaps the most powerful clue. It has been narrowed down to an accent that was likely developed in the South East area of Greater London. Linguists determined he is likely under 30 based on his voice, and his youth was spent studying in Southern London. They believe he is educated to at least a completed high school level

Experts will try to determine if he lived all of his life in Britain or moved around — that will be more of an art than a science, as experts can and have disagreed on the matter. A forensic voice expert told CNN that British intelligence authorities will now work to match his voice to existing recordings. With any luck, they will be able to narrow down his voice to between 200 and 300 matches

The voice is also being used to try and determine John's ethnicity. Paul Kerswill, a linguistics expert at the University of York, told CNN, "It's quite hard to tell the ethnicity of this person from his voice alone. He's probably not British white. He could be of Pakistani origin; he could be of Somali origin; he could be South American origin or something. It's very, very hard to pinpoint." 

The actual words John spoke in the video are also of importance. They may, however, have been written by someone else. "Some of the phrasing is not pure native speaker, so he's been assisted with this text. It's not entirely him," said Kerswill. 

Christopher Voss, a Georgetown University professor who spent 24 years as a lead hostage negotiator for the FBI, told The Wire that the language used both in the threat against another hostage's life and the longer anti-American speech aimed to show superiority. 

Voss notes this excerpt from John's speech: 
You are no longer fighting an insurgency; we are an Islamic Army and a state that has been accepted by a large number of Muslims worldwide, so effectively, any aggression towards the Islamic State is an aggression towards Muslims from all walks of life who have accepted Islamic Caliphate as their leadership." 
"They are very clearly trying to show that this is a rightful punishment because it was decreed by the state," says Voss. "They need to show they are the power in the Middle East. With the wording, they want to show they are more powerful than Obama." 
 

In order to best assist hostage Steven Sotloff, intelligence organizations will look to pinpoint the time and place of the recording to find out which devices were online. Weather patterns and shadows will help determine locations, however, an expert told Bloomberg News it may be easier to tell the time than the exact place because of the plain desert background of the video. That could also involve tapping into the massive database of NSA and GCHQ intercepts of electronic communications from the region.

As for the final identification, Prime Minister David Cameron has already said it is likely that John is a British citizen. Anil Jain, a professor of biometric recognition techniques at Michigan State University, told Bloomberg News this means it is "likely he is in the passport office database." 

Update (8/24): Over the weekend, British Intelligence services allegedly identified "John" as Abdel-Majed Abdel Bary, a 23-year-old man originally from London. Read more here.