A British national accused of taking a leading role in a scheme by so-called Islamic State is standing trial in the United States.
He is the last of four Brits believed to have been part of a terror gang dubbed "the Beatles" to have his fate decided, with two already facing the justice system and another killed.
El Shafee Elsheikh faces a potential life sentence, with allegations he was involved in the death of two British citizens, among others.
Who are the so-called IS Beatles?
Elsheikh, 33, was one of a gang of four IS militants nicknamed “the Beatles” by their captives due to their British accents.
The cell – said to be made up of ringleader Mohammed Emwazi, known as Jihadi John, Aine Davis, Elsheikh and Alexanda Kotey – was allegedly responsible for the brutal killings of a number of Western and Japanese captives, including Britons Alan Henning and David Haines.
Emwazi was killed by a US drone strike in 2015 while Davis is serving a sentence in a Turkish jail. Kotey, meanwhile, has already pleaded guilty.
The slayings sparked outrage and revulsion around the world after being broadcast in graphic detail.
Kotey and Elsheikh had taken part in and been arrested during a demonstration outside the US embassy in London in 2011 in support of the 9/11 attacks.
They travelled to Syria the following year.
What’s Elsheikh charged with?
He is charged in the US as a leading participant in “a brutal hostage-taking scheme targeting American and European citizens" from 2012 through 2015.
He is specifically charged with conspiring in the kidnapping and deaths of four Americans - journalists James Foley and Steven Sotloff, and aid workers Kayla Mueller and Peter Kassig.
Foley, Sotloff and Kassig were all beheaded. Mueller was tortured and raped by Islamic State leader Abu Bakr Al-Baghdadi before she was killed.
In a 2019 interview, Elsheikh told ITV News he wants to be taken to the UK rather than stand trial in the US
Elsheikh's lawyers tried to have the charges thrown out before trial, arguing that confessions made by Elsheikh and Kotey were given under duress. But a judge rejected those arguments.
He said the evidence shows that confessions made both to government interrogators and to journalists were made freely.
Elsheikh faces a potential life sentence - the government agreed not to seek the death penalty to obtain his extradition.
While the majority of charges against Elsheikh revolve around the killing of the four Americans, the indictment also holds him responsible for his role in the deaths of Mr Haines and Mr Henning.
What happened to Alexanda Kotey?
Kotey, 37, who grew up in London, attended a two-hour change of plea hearing at US District Court in Alexandria, Virginia, in September and pleaded guilty to eight charges.
The charges were:
four counts of hostage taking resulting in death
conspiracy to commit hostage taking resulting in death
conspiracy to murder United States citizens outside of the United States
conspiracy to provide material support to terrorists – hostage taking and murder – resulting in death
conspiracy to provide material support to a designated foreign terrorist organisation resulting in death.
Kotey has agreed to fully co-operate with authorities as part of his plea agreement, the court was told last year.
'This trial means everything': David Haines' daughter, Bethany, tells ITV News this is a chance for justice
He is scheduled to be sentenced in April.
Who were the Brits allegedly killed by the cell?
Former aircraft engineer and humanitarian Mr Haines, 44, from Perth in Scotland, was beheaded in Syria in 2014 after being held prisoner for 18 months.
Cab driver-turned-aid worker Mr Henning, 47, from Lancashire, was also beheaded in 2014 after being captured by extremists in Syria.
What have victims’ families said?
Diane Foley, mother of slain US hostage James Foley, said it was “chilling” being in court with Kotey, and urged the Briton to give up information about the Beatles’ atrocities.
She told the Today programme on BBC Radio 4: “I didn’t get any indication he’s interested in (making amends) but I hope in time he might, just because the extent of the evil he has committed is – I just don’t know how any soul could live with all that.
“All of us would like to know where the remains of our children are.”
Ahead of a hearing in November last year, Bethany Haines said she 'wouldn't be intimidated' by Elsheikh
Bethany Haines, daughter of humanitarian Mr Haines, echoed the plea.
She told ITV News: “We are glad Alexanda Kotey has finally admitted his guilt and justice will be served.
“It’s been a hard few years and there will be hard times to come but my family and I would like to bring my dad home to rest.
“We ask Kotey and Elsheikh to please give us the closure we desperately need and tell us what happened and where my dad’s remains are.”
Kotey claims he was not physically present at any of the killings of the Western captives.
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