Security services are likely to attempt to match the voice of James Foley's killer to a database of terror suspects' voices, a forensic voice and speech analyst has told ITV News.
Elizebeth McClelland told ITV News experts the first thing investigators would have to do would be to find "reference samples" from a database, before those could be automatically matched against the voice heard in the shocking Islamic State video.
She added that the process could be made "reasonably quick" by analysing the detail of vowel and consonant sounds, rhythm, pitch, intonation and voice quality - though the evidence gained would only be "part of a bigger jigsaw" to identify the suspect.
A British family have told ITV News of their devastation after discovering a close relative is fighting with the Islamic State in Iraq.
A French journalist who was held hostage with James Foley in Syria has told ITV News it was "devastating" to see his murder.