"60 MINUTES" REVEALS THE IDENTITY AND SHOWS VIDEO OF THE SOURCE KNOWN AS "CURVE BALL," WHOSE TALL TALE OF IRAQI MOBILE BIOLOGICAL WEAPONS WAS CRUCIAL IN THE U.S. DECISION TO GO TO WAR IN IRAQ -- SUNDAY ON CBS

60 MINUTES has identified the man whose fabricated story of Iraqi biological weapons drove the U.S. argument for invading Iraq. It has also obtained video of "Curve Ball," as he was known in intelligence circles, and discovered he was not only a liar, but also a thief and a poor student instead of the chemical engineering whiz he claimed to be. Bob Simon's two-year investigation will be broadcast on 60 MINUTES Sunday, Nov. 4 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

Curve Ball is an Iraqi defector named Rafid Ahmed Alwan who arrived at a German refugee center in 1999. Click here to see an image of Alwan. To bolster his asylum case and increase his importance, he told officials he was a star chemical engineer who had been in charge of a facility at Djerf al Nadaf that was making mobile biological weapons. 60 MINUTES has learned that Alwan's university records indicate he did study chemical engineering but earned nearly all low marks, mostly 50s. Simon's investigation also uncovered an arrest warrant for theft from the Babel television production company in Baghdad where he once worked. Also appearing in Sunday's segment is video that 60 MINUTES obtained of Alwan at a Baghdad wedding in 1993 - the first time images of him have ever been made public.

He eventually wound up in the care of German intelligence officials to whom he continued to spin his tale of biological weapons. His plan succeeded partially because he had worked briefly at the plant outside Baghdad and his descriptions of it were mostly accurate. He embellished his account by saying 12 workers had been killed by biological agents in an accident at the plant. More than a hundred summaries of his debriefings were sent to the CIA, which then became a pillar - along with the now-disproved Iraqi quest for uranium for nuclear weapons - for the U.S. decision to bomb and then invade Iraq. The CIA-director George Tenet gave Alwan's information to Secretary of State Colin Powell to use at the U.N. in his speech justifying military action against Iraq.

Tenet gave the information to Powell despite a letter - a copy of which 60 MINUTES obtained -- addressed to him by the head of German intelligence stating that Alwan appeared to be believable, but there was no evidence to verify his story. Through a spokesman, Tenet denies ever seeing the letter. "[Tenet] needs to talk to his special assistants if he didn't see it," says Tyler Drumheller, a former CIA senior official. "I am sure they showed it to him and I am sure...it wasn't what they wanted to see," he tells Simon. Other CIA officials doubted Curve Ball's authenticity, including former Central Group Chief Margaret Henoch, who speaks publicly for the first time, telling Simon she openly refuted Alwan's story. "And it was like 'Whack a Mole.' He just popped right back up. It was unbelievable."

Alwan was caught when CIA interrogators were finally allowed to question him and confronted him with evidence that his story could not be as he described it. Weapons inspectors had examined the plant at Djerf al Nadaf before the fall of Baghdad and found no evidence of biological agents.

In the end, however, Alwan got what he wanted. He is believed to be in Germany, free and probably living under an assumed name. Why did he do it? "It was a guy trying to get his green card essentially, in Germany, and playing the system for what it was worth," says Drumheller. "It just shows...the law of unintended consequences," he tells Simon.