Rogers Clemens

The prosecution's star witness underwent a withering cross-examination on Thursday at Roger Clemens' perjury trial. Clemens, a seven-time Cy Young Award winner, is charged with lying to Congress when he testified that he never used performance-enhancing drugs. Brian McNamee, his one-time trainer, is the only witness who has firsthand evidence that contradicts the baseball-pitching ace.

Earlier this week, guided by the prosecution, McNamee testified in agonizing and repetitive detail about how he injected Clemens with steroids and human growth hormone between 1998 and 2001.