CSI: Crime Scene Investigation (2000)

S04E20 Dead Ringer

Grissom, Catherine, and Nick look into the fatal incident of a runner who collapsed during a race. Simultaneously, Sara and Warrick probe the deaths of a couple found in a hotel room, which is initially suspected to be a murder-suicide. Both investigations unfold during a massive police competition that attracts over 20,000 officers, adding a unique twist, as nearly all the victims and potential suspects are law enforcement personnel.