Ahmed Saadat, 52, had been secretary-general of the Popular Front for the Liberation of Palestine (PFLP) for only a short while when he was arrested in connection with the killing of right-wing Israeli Tourism Minister Rehavam Zeevi by PFLP gunmen in 2001.
Saadat originally trained as a teacher
The attack itself was to avenge the assassination of Mr Saadat's predecessor, Abu Ali Mustafa, by Israel.
Mr Saadat - a second-generation PFLP leader - has been in Palestinian custody since early 2002.
He is the highest-ranking Palestinian political figure arrested by the Palestinian Authority.
He was moved to Jericho under international supervision in a deal to lift Israel's siege of Yasser Arafat's Ramallah compound in May 2002.
He belongs to what is known as the movement's "insiders", those who stayed in the West Bank and Gaza rather than going into exile.
Mr Saadat, who trained as a maths teacher, is a veteran of the first Palestinian intifada. Before being arrested by the Palestinians, he had spent some 10 years in Israeli jails, on eight separate occasions.
It is reported that it was his work with other detainees that led to his appointment to the PFLP's ruling body, its politburo.
"He has good contacts and is a man of the people. He is a charismatic figure," Abdul Bari Atwan, editor of pan-Arab newspaper al-Quds al-Arabi, said at the time of his arrest.
His predecessor, Abu Ali Mustafa, was a member of the "old guard" of exiled leaders based in the Syrian capital, Damascus.
Saadat's predecessor, Abu Ali Mustafa, was assassinated by Israel
As a result, analysts say Mr Mustafa was not as familiar with the situation on the ground in the Palestinian territories as his successor and was not thought to have had the full backing of the PFLP membership.
Mr Saadat took over as leader of the PFLP in October 2001, two months after Mr Mustafa was assassinated in an Israeli attack on his office.
His election was widely seen as a move to consolidate the PFLP's presence in the West Bank and Gaza.
Mr Mustafa's move back to the Palestinian territories under Yasser Arafat's Palestinian Authority was seen as an indirect acceptance of the Oslo peace plan negotiated with Israel.
Mr Saadat, however, was seen as a more radical leader and more loyal to the "original" principles of PFLP founder and former leader George Habash.
When he took over the reins of the PFLP, Mr Saadat vowed to avenge the assassination of Mr Abu Ali.
Shortly afterwards, the group assassinated Rehavam Zeevi.
This, analysts say, was a popular move among militants and one that reinvigorated the organisation.
The PFLP combines Arab nationalism with Marxist Leninist ideology and sees the destruction of Israel as integral to its struggle to remove Western influence from the Middle East.