The judge overseeing the perjury trial in Washington of former star major league baseball pitcher Roger Clemens has declared a mistrial over inadmissible evidence shown to the jurors.

U.S. District Judge Reggie Walton said Thursday that Clemens could not be assured a fair trial after prosecutors showed jurors evidence against his orders during the second day of testimony.

They played a video from Clemens' 2008 appearance before Congress in which he denied the use of banned, performance-enhancing drugs. But the video shows close friend and former New York Yankees' teammate Andy Pettitte saying Clemens told him he did use human growth hormone in 1999 and 2000. Pettitte said he told his wife about the conversation the same day it happened.

Prosecutors had wanted to call Laura Pettitte as a witness to back up her husband's account. But the judge said he was not inclined to allow her to testify since she had not spoken directly to Clemens.

Walton has scheduled a hearing September 2 to determine whether to hold a new trial.

Raising his voice and noting that the case has already cost a lot of taxpayer money, Judge Walton said “government counsel should have been more cautious.''

The 48-year-old Clemens pitched for the New York Yankees, Boston Red Sox, Toronto Blue Jays and Houston Astros during a stellar 24-year career. He was a seven-time winner of the Cy Young award, which annually honors the best pitcher in each league.

Clemens is one of only four pitchers to strike out more than 4,000 batters.