Al-Tikriti was a leading figure in the Mukhabarat, the intelligence service that later turned to another agency performing the duty of Secret Police, from the 1970s, later taking over as director. During his time in the secret police, al-Tikriti played a key role in the Iraqi regime's execution of opponents at home and assassinations abroad. He was also known for his ruthlessness and brutality in purging the Iraqi military of anyone seen as disloyal.
Al-Tikriti became Iraq's representative to the United Nations in Geneva—including the UN Human Rights Committee—in 1989. He was in Geneva for almost a decade, during which he is believed to have managed clandestine accounts for the Iraqi president's overseas fortune. This task was then taken over by a network of foreign brokers, since Hussein had decided that no one in Iraq could be trusted with this task.
U.S. officials characterized al-Tikriti as a member of what they called "Saddam's Dirty Dozen", responsible for torture and mass murder in Iraq. U.S. forces captured him on 17 April 2003. Al-Tikriti was the five of clubs (queen of hearts according to CNN) in the most-wanted Iraqi playing cards.
Barzan Mohamed's trial started on 19 October 2005. He was a defendant in the Iraq Special Tribunal's Al-Dujail trial, and Abd al-Semd al-Husseini was his defence counsel. In a first stage, Al-Tikriti stood trial before a five-judge panel for the Dujail Massacre. He was charged for crimes against humanity, simultaneously with seven other former high officials (Taha Yassin Ramadan, Saddam Hussein, Awad Hamed al-Bandar, Abdullah Kadhem Roweed Al-Musheikhi, Ali Daeem Ali, Mohammed Azawi Ali and Mizher Abdullah Roweed Al-Musheikhi). They were said to have ordered and overseen the killings, in July 1982, of more than 140 Shi'ite men from Dujail, a village 35 miles north of Baghdad. The men were allegedly killed in retribution after an 8 July 1982 attack on the presidential motorcade as it passed through the village. It was alleged that, apart from the killings, hundreds of women and children from the town were jailed for years in desert internment camps, and that the date palm groves, which sustained the local economy and were the families' livelihood, were destroyed.
During the first court session on 19 October 2005, al-Tikriti pleaded not guilty. During his trial, he was known for his angry outbursts in court and was ejected on several occasions.
In the weeks following the first audience, serious security concerns for the defense team of Hussein and the other accused became apparent. On 21 October 2005, 36 hours after the first hearing, a group of unidentified armed men dragged one of the attorneys from his office in east Baghdad and shot him dead. A few days later, a second lawyer was killed in a drive-by shooting, and a third, injured in that attack, subsequently fled Iraq for sanctuary in Qatar.
As a result, calls for the trial to be held abroad were heard. The defense lawyers, supported by the Iraqi Bar Association, imposed a boycott on the trial until their security concerns were met with specific measures. A few days before the trial was to resume, the defense team announced that it had accepted offers of protection from Iraqi and U.S. officials and would appear in court on 28 November 2005. The agreement is said to have included the same level of protection that is offered to the Iraqi judges and prosecutors, with measures such as armored cars and teams of bodyguards.
After a short court session on 28 November 2005, during which some testimony regarding the killings in Dujail was presented, Judge Rizgar Mohammed Amin ordered a one-week adjournment until 5 December, to grant the defence teams time to find new counsel.
On 12 March 2006, the prosecutor announced that if Hussein and his seven co-defendants were sentenced to death in the Dujail case, the sentence would be carried out as soon as possible. Thus, the other cases for which they were indicted would not be heard in court. On 19 June 2006, the prosecutor asked the court, in his closing arguments, that the death penalty be imposed upon al-Tikriti, Hussein and Ramadan.
On 5 November 2006, al-Tikriti was sentenced to death by hanging. On 15 January 2007, the death sentence was carried out. Al-Tikriti, along with co-defendants Hussein and the former Chief Justice of the Iraqi Revolutionary Court al-Bandar, was sentenced to death by hanging. He was originally scheduled to hang on 30 December with Hussein (as he and al-Bandar wished) but due to the Eid, lack of time, and lack of a helicopter to deliver them, as well as international pressure, the hangings were postponed to 15 January. Al-Tikriti's sentence was carried out at 03:00 local time (00:00 UTC) on 15 January 2007. His death was confirmed at 3:05/00:05 UTC. Barzan was decapitated by the long drop, the accidental result of the hangman using a rope that was too long. Al-Tikriti's and al-Bandar's counsel was not allowed to attend, as was the case with Hussein's hanging.