Roger Clemens was acquitted Monday on all charges that he obstructed and lied to Congress in denying he used performance-enhancing drugs to extend his career as one of the greatest pitchers in baseball history. Clemens was quietly emotional after the verdict was announced. "I'm very thankful," he said, choking up as he spoke. "It's been a hard five years," said the pitcher, who was retried after an earlier prosecution ended in a mistrial.