Correspondent Scott Pelley has an interview with Greg Thielmann, a former expert on Iraqi weapons of mass destruction. Thielmann, a foreign-service officer for 25 years, now says that key evidence in the speech was misrepresented and the public was deceived.
"I had a couple of initial reactions. Then I had a more mature reaction," says Thielmann, commenting on Powell's presentation to the United Nations.
"I think my conclusion now is that it's probably one of the low points in his long, distinguished service to the nation."
Thielmann's last job at the State Department was director of the Office of Strategic Proliferation and Military Affairs, which was responsible for analyzing the Iraqi weapons threat for Secretary Powell. He and his staff had the highest security clearances, and everything - whether it came into the CIA or the Defense Department - came through his office.
Check out the interactive for tracing various claims Powell made in that speech.