Demonstrators in support of the Islamic State rally in Mosul in 2014.

Demonstrators in support of the Islamic State rally in Mosul in 2014. AP file photo

Charts: Who Are the Americans Accused of Joining ISIL?

Despite research, there is no one "profile" that they all fit.

The militant group that calls itself the Islamic State recruits foreign fighters—more than 20,000 to date, according to some estimates—from all over the world, France to Indonesia. And some of those, of course, are from the United States.

Though estimates vary and the data is difficult to obtain, at least 30 to 40 American fighters seem to be currently affiliated with the islamists in Syria and Iraq. A new study from the Center on National Security from Fordham University’s School of Law found that 56 people in the United States have been charged with crimes related to supporting ISIL between March 2014 to June 2015, and three associated people had been killed.

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Most of these cases are still at various stages of the judicial process, and only four have received sentences, ranging from four years to 20. Some critics have questioned the FBI’s investigation tactics, and expressed doubt that all of those charged would actually have pursued violent ends without the coaxing and goading of intelligence agency operatives.

The rate of arrests on US soil accelerated quickly after ISIL took over major Syrian cities in January 2015: from one arrest on average per month it went to seven. Since March 2015, the number of domestic plotters charged has also sharply increased—15 out of 17 were identified or indicted since March 2015.

Most of the recruits are fairly young, with the average age of 26 and the median age of 24, but other than that there is no overarching profile that emerges from the group. They come from a range of ethnic backgrounds, and at least a third are converts to Islam. Only 14% of them had a previous felony conviction.

Three of those who were charged made it to Syria to join ISIL. Many of them communicated with the group through social media (80%), and at least 18 of the individuals were identified by the authorities due to their activity on Twitter or Facebook.

About two-thirds, 64%, of the US recruits were born in the US, and 81% are American citizens.