Ground Zero - S4-E14
Other mistake: When Hawke blows up Yahara's plane, we see that the video feed in the holding cell where Locke, Santini, and Rivers are is actually from a 3rd person perspective and that it continues, but according to previous dialogue (and video up to that point) the camera was installed on the plane, so once Hawke blew the plane up, there should have been no more video feed. (00:40:35)
Other mistake: General Butarra holds his pistol to St. John's head asking him where the diamonds are, dry firing it when he doesn't tell him, so the chamber must be empty. He then proceeds to load a magazine into the gun, but never chambers a round, and then proceeds to shoot the radio when it receives a storm alert broadcast. (00:28:40 - 00:29:11)
Answer: No truth serum has proven to make a person tell the truth. Regarding capturing Mace, and forcing him to tell him where St. John is by water boarding him, People subject to torment such as water boarding are not likely to tell the truth, so Mace would probably lie.