Season 6 Episode 14 - Smoke & Mirrors

When SG-1's old "friend" Senator Kinsey is assassinated, O'Neill becomes the lead suspect with indisputable evidence against him - a surveillance camera that took his picture and the murder weapon in the lake near his cabin where he was purportedly fishing. Sam goes to the NID and teams up with an agent Barrett, while Teal'c interrogates a prisoner and Jonas deduces that the transformation devices (last seen in Foothold) were used to frame Jack. Sam and Barrett discover a conspiracy of secret businessmen that gained access to the devices at Area 51 and stole them. Revealing that Kinsey survived the attack, Sam and Barrett use his presence as a decoy - one of the conspiracy's agents sends a man transformed into Major Davis but they thwart him and Sam, hologrammatically disguised as the killer, arrests them all. Jack is cleared but Kinsey reveals that he plans to use the sympathy used by the assassination attempt, and Jack's reputation, to cement his own reputation as he makes a run for the Presidency.