Emerging from his Islamabad mansion on Feb. 6, A. Q. Khan looked victorious; after five years of de facto house arrest, the Pakistani government declared that the nuclear scientist was being set free. Unfortunately for the rest of the world, Khan's life's work which included a clandestine network that sold nuclear secrets to nations such as North Korea, Iran and Libya is still holding the rest of the world hostage. And while Khan is viewed by many in Pakistan as a national hero for developing the country's nuclear weapons program, his rogue dealings have simultaneously helped advance nuclear proliferation in some potentially dangerous hotspots. (Read TIME's A. Q. Khan cover story "The Merchant of Menace"
The A.Q. stands for Abdul Qadeer.
Was born in India in 1936 and immigrated to Pakistan in 1952 where he attended college and worked briefly as a postal inspector. He then moved to Europe where he earned engineering and metallurgy degrees and studied nuclear power.
Is married to a South African-Dutch woman named Henny. They have two daughters.
Reportedly speaks many languages, including Dutch, German, English, Urdu and Hindi, as well as basic French and Persian.
After India detonated underground nuclear bombs in 1974, Khan sent word to Pakistan's leader, Zulfikar Ali Bhutto, offering to help Pakistan build its own nuclear program. While working at a Dutch company where he had high security clearance, Khan had copied and photographed nuclear designs, which he brought back to Pakistan.
When Pakistan detonated a series of underground nuclear bombs in 1998, Khan was hailed as a hero India already had nuclear weapons and Pakistan's acquisition was seen as leveling a contentious playing field. Khan's portrait was painted on buses and he was awarded the Hilal-e-Imtiaz medal, which honors Pakistanis of outstanding achievement.
While being celebrated as a national hero, Khan was secretly selling nuclear secrets and centrifuges to other countries, including North Korea, Iran and Libya, according to the International Atomic Energy Agency.
At one point, Khan was worth some $400 million. With his clandestine income, Khan became a multimillionaire who collected vintage cars and foreign properties. Outside his mansion in Islamabad, he had a jasmine bush trimmed into the shape of a mushroom cloud.
In 2003, after British and United States intelligence officials intercepted a ship headed for Libya with centrifuge parts from Khan, Libyan leader Muammar Gaddafi, caught red-handed, decided to give up his nuclear program and cooperate with international inspectors.
On Feb. 2, 2004, Khan appeared on Pakistani national television and confessed to operating a clandestine network that sold nuclear secrets. Then President Pervez Musharraf pardoned him the next day and Khan was placed under de facto house arrest. While the Pakistani government claimed he was being held for his own protection, Khan was not allowed to move freely.
According to the Pakistani government, Khan was diagnosed with prostate cancer in August 2006.
On May 30, 2008 Khan said that his 2004 televised confession was a lie and that he had been pressured by Musharraf into making it. The same year, according to the Associated Press, the Pakistani government ordered Khan not to discuss nuclear weapons technology with anyone, including his family.
"We were inside his residence, inside his facilities, inside his rooms...We were everywhere these people were."
CIA Director George Tenet in a 2004 speech about Khan and the U.S. government's monitoring of his movements.
"It has to be pulled up by its roots and examined to make sure we have left nothing behind."
Colin Powell, secretary of state, after Khan confessed on TV to operating a secret nuclear proliferation network, Associated Press, Feb. 9, 2004
"The so called A. Q. Khan affair is a closed chapter.
Pakistani government official statement on Khan's release, Associated Press, Feb. 6, 2009
''All Western countries...are not only the enemies of Pakistan but in fact of Islam.'' "
New York Times January 4, 2004
"I take full responsibility for my actions and seek your pardon."
in his 2004 televised confession, BBC, Feb 20, 2004
"At least I have got my freedom. I can move around...I don't care about the rest of the world. I care about my country."
upon his release from house arrest, Associated Press, Feb. 6, 2009
(See Photos of A.Q. Khan's Nuclear Connections)