US prosecutors have accused a former US Air Force officer of spying for Iran in an elaborate operation that targeted her fellow intelligence officers.
But who is Monica Witt?
Details of her upbringing are unclear, but a previously issued FBI missing persons poster says that she was born on 8 April 1979 in El Paso, Texas.
According a curriculum vitae posted on jobs website Indeed, Ms Witt joined the Air Force in December 1997. Stationed at Offutt Air Force Base, she worked as a Persian-Farsi language specialist.
She later served as a Special Agent at the Air Force's Office of Special Investigations (AFOSI) from November 2003, based at Andrews Air Force Base in Maryland. On its website, the AFOSI says its mission is to "identify, exploit and neutralize criminal, terrorist and intelligence threats to the Air Force, Department of Defense and U.S. Government".
According to the indictment, Ms Witt was privy to classified information that could identify US intelligence officers and their sources.
A spokesperson for the US Air Force told the BBC she was discharged in June 2008 with the rank of Technical Sergeant. She received numerous decorations including the Air Medal, awarded for "single acts of heroism or meritorious achievements".
Ms Witt left the US military in May 2008. For the next seven months, she worked as a contractor with Booz Allen Hamilton in Maryland, consulting on "Iranian subject matter" and providing "language and cultural specialisation".
From November 2008 to August 2010, she worked as a Middle East Desk Officer at another contractor, Chenega Federal Systems, in Virginia. During this role Ms Witt says she "supervised, controlled, and co-ordinated the execution of highly sensitive counterintelligence operations against foreign intelligence services worldwide".
Later, from December 2010 to May 2011, Ms Witt worked in Washington with Amidest. During her time with the non-profit group, she "submitted applications for 60 Iraqi Fulbright candidates to multiple US universities".
'Injustice to Muslims'
According to her CV, she holds a bachelor's degree from the University of Maryland, a master's from George Washington University, and a qualification in Persian-Farsi from the Defense Language Institute.
George Washington University's International Affairs Review published two articles by Ms Witt in 2012. In one, she criticised the US for calling on Iran's neighbours to sever relations with Tehran.
"In enacting a policy of severe sanctions against Iran, the US should address the potential affects (sic) on other countries and not inadvertently alienate friends by making them choose between Iran and the US" wrote Ms Witt.
According to her online CV, she lived and worked within countries including Iraq, Qatar, Jordan, Turkey, the UAE, Tajikistan and Iran.
After this, details of her activities and whereabouts are unclear.
In an undated missing persons declaration the FBI says MS Witt worked as an English teacher in either Afghanistan or Tajikistan and had been out of contact since 2013.
According to her indictment, in early 2012 Ms Witt converted to Islam during a ceremony broadcast on Iranian television. In several other television appearances, she allegedly identified herself as a US veteran and made statements critical of the US government.
State-run Press TV also published an article by Ms Witt, in which she attacked "a prevailing culture of tolerance for sexual harassment" within the US armed forces.
In February 2012, Ms Witt allegedly went to a "Hollywoodism" conference in Iran organised by the New Horizon Organization. The Justice Department says the event seeks to promote "anti-American propaganda".
A few months later, the FBI warned her that she was targeted for recruitment by Iranian intelligence services.
The following year, Ms Witt was quoted in an article by the International Quran News Agency where she discussed her conversion to Islam and American "injustice to its Muslim population".
"As someone who served in the US army for years, I expected that after embracing Islam, my right to choose a religion and my beliefs would be respected," she said.
"However, a US army member becoming Muslim was not something they could stand. They are afraid of such individuals."
In summer 2013, Ms Witt had an "ideological" turn, the indictment says, and tried defecting to Iran through its embassy in Kabul.
She later moved Iran and allegedly disclosed highly classified information to Iranian officials. The information included details of her former colleagues and their informants.
A warrant has been issued for Ms Witt, who remains at large.