As a senior, he helped the Tigers post their best-ever record of 13–1, and advance to the Oklahoma Class 4A state championship game.
[citation needed] He ended his senior season with 151 tackles, 3 interceptions, 2 sacks, and 3 forced fumbles.
Memorably, he caught the interception by Texas quarterback Chris Simms which was jarred loose by Roy Williams and Lehman took it into the endzone for the game clinching score.
In 2002, Lehman moved to weakside linebacker, replacing Butkus Award winner Rocky Calmus.
Lehman was recognized as a consensus first-team All-American, after receiving first-team honors from the Associated Press, the Football Writers Association of America, the Walter Camp Foundation, The Sporting News, CNNSI, ESPN and Sports Illustrated.
[2] He posted six tackles (five unassisted) in the Rose Bowl against Washington State and sacked quarterback Jason Gesser twice for a loss of 17 yards.
Lehman closed out his college career in the 21–14 Sugar Bowl loss against the LSU Tigers with eight tackles (six solo) and two stops behind the line of scrimmage, including one sack.
Lehman was rated the top outside linebacker pro prospect in the country by The NFL Draft Report.
Lehman was signed by the Buffalo Bills on November 7, 2008, after cornerback Ashton Youboty was placed on injured reserve.