Crimes and Witch-Demeanors - S6-E19
Other mistake: At the end, it shows the Charmed Ones orbing out of the trial, but Chris and Leo never leave. Right after the Charmed Ones orb out, Barbas begins discussing his evil plans with Gideon, so wouldn't Leo and Chris find out that Gideon is plotting against them? After they talk, the camera pans out and Chris and Leo are not there. I guess they just forgot to put in the scene where they leave.
Answer: "Hush, Hush, Hush" Paula Cole.