Abid Hamid Mahmud al-Tikriti was one of Saddam Hussein's closest confidants.
Tikriti was one of Saddam's closest aides
He was the deposed leader's presidential secretary and ranked fourth on America's list of 55 most wanted Iraqi fugitives.
Mahmud al-Tikriti featured as the ace of diamonds in the US pack of playing cards depicting wanted members of the former regime.
A former non-commissioned officer in Saddam Hussein's bodyguard, Mahmud al-Tikriti rose through the ranks to become a lieutenant general, before Saddam Hussein picked him as his right-hand man.
Mahmud al-Tikriti - a distant cousin of Saddam Hussein - was third in power to the former president and was frequently seen at his side.
Some observers placed him as high as second-in-command.
"He was Saddam's key adviser and his responsibility included overseeing basically any issue of importance to Saddam, particularly regime security," an unnamed US official told French news agency AFP.
He decided who met Saddam Hussein and is said to have been one of the few people the Iraqi leader truly trusted.
Mahmud al-Tikriti is said to have directed matters of state and handed down many of the regime's repressive orders.
US officials believe Mahmud al-Tikriti might have information about Saddam Hussein's fate following the end of the US-led war in April, and knowledge of his alleged weapons of mass destruction programme.
In the 1990s, the presidential was put in charge of places in Iraq where coalition forces suspect Saddam Hussein might have concealed banned weapons.
US officials have said they want to put Mahmud al-Tikriti on trial for war crimes or crimes against humanity, allegedly committed during the period of Saddam Hussein's rule.