Ex-trainer to return to stand in Clemens perjury trial WASHINGTON (Reuters) - The star prosecution witness in Roger Clemens' perjury trial will return for a second day of testimony on Tuesday with more vivid details expected about the former baseball pitcher's alleged use of performance-enhancing drugs. Brian McNamee, whose testimony is crucial to prosecutors' charges that Clemens lied to Congress about his alleged drug use, gave jurors a detailed description on Monday of injecting Clemens with anabolic steroids while with the Toronto Blue Jays in 1998. McNamee, the player's former trainer, is expected to describe Clemens' alleged use of performance-enhancing drugs after the pitcher joined the New York Yankees in 1999. McNamee has said he injected Clemens, considered one of the best pitchers to ever play the game, with anabolic steroids in 1998, 2000 and 2001, and human growth hormone in 2000. A former Major League Baseball strength coach, McNamee worked with Clemens when the right-hander pitched for the Blue Jays and later with the Yankees. He also worked as Clemens' personal trainer. Clemens' lawyers have labeled McNamee a liar and are expected to explore his alleged problems with alcohol and scrapes with law enforcement. Whether the jury in U.S. District Court believes McNamee will be a major factor in determining the trial's outcome. He is expected to spend several days on the stand. Clemens, 49, is being tried for a second time on federal charges of lying to the House of Representatives' Committee on Oversight and Government Reform in 2008, which was probing drug use in baseball. Clemens is a record seven-time winner of the annual Cy Young Awards as best pitcher and played for 24 years in the major leagues. He is among the biggest names implicated in drug use in baseball. The trial is starting its fourth week.