"It's like any other crime; there's lots of little clues, and if you know where to look for them, they can help you solve the crime," the counterterrorism expert told FoxNews.com. "It's like looking for fingerprints, it's the same thing."
Voice analysis, in particular, could prove crucial.
"Linguistic technology is very good nowadays at matching voice characteristics," said Ashraf. "If [the killer] has got a criminal background, there's a very good chance that he could have been interviewed by police." Voice recognition software could be used to compare the militant's speech in the YouTube video to police recordings, he explained.
The expert also noted that the killer's accent could prove valuable clues as to his identity. "There are speech experts who specialize in accents who are very good about identifying this information, both in terms of geography and ethnic group," he said. "Your voice is partly shaped by your ethnic background."