IS "Beatle" El Shafee Elsheikh has been found guilty of his role in a brutal hostage-taking scheme and conspiring to murder journalists and aid workers.
The 33-year-old Brit was linked to the abduction, torture and beheading of numerous hostages in Syria.
Prosecutors convinced the jury that Elsheikh, known as "Ringo", had been part of the cutthroat collective horrifically killing civilians.
The foursome were dubbed the 'ISIS Beatles' by their captives because of their British accents.
The bloodthirsty group were accused of kidnapping and torturing 26 Western hostages between 2012 and 2015.
The jury in Alexandria, Virginia, delivered a guilty verdict less than six hours after the two-week trial after hearing the harrowing details of torture.
Elsheikh was charged with hostage-taking, conspiracy to murder US citizens and supporting a terrorist organization.
He will now faces up to life in prison for his role in the deaths of four Americans who were taken captive.
The US will not seek the death penalty against him.
Journalists James Foley and Steven Sotloff, and aid workers Kayla Mueller and Peter Kassig were killed by the Islamic State terror cell.
"The Beatles" are also said to be responsible for the deaths of British aid workers David Haines and Alan Henning, and Japanese journalists Haruna Yukawa and Kenji Goto.
Foley, Sotloff and Kassig were decapitated, while Mueller was forced into slavery and raped repeatedly by Islamic State leader Abu Bakr al-Baghdadi before being killed as well.
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David Haines was also beheaded in September 2014.
John Cantlie is still missing and is presumed to be in the hands of the Islamic State, almost a decade after he was kidnapped.
Horrific footage of some of their deaths was chillingly shared on social media, in another blow to the victim's families.
Jurors deliberated for less than six hours in total before delivering their verdict on Thursday afternoon.
Elsheikh's lawyers insist he was just a "simple ISIS fighter" who wasn't involved in the torture carried out by "The Beatles".
Surviving hostage Federico Motka, an Italian-born aid worker, told the court of his 14-month ordeal at the hands of the four Jihadis.
He was kidnapped near a refugee camp on the Turkish border and taken to Syria in March 2013.
In chilling testimony, he claimed Elsheikh, 'George', and 'John' made him and three other prisoners take part in a 'Royal Rumble'-style fight with each other for their pleasure.
suits with numbers on the back similar to those worn by inmates at Guantanamo Bay, to 'remind' them of the US prison.
Mohammed Emwazi, the ISIS executor known as 'Jihadi John', was killed in a drone strike in 2015, while Alexanda Kotey and Elsheikh were captured in Syria in January 2018 and brought to Virginia to face trial.
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Last year, Kotey pleaded guilty in a plea bargain that calls for a life sentence.
Under the agreement, he will serve 15 years in jail in the US and will then be sent to the UK to face further charges.