Doubt is one of the options given to judge a statement during an interrogation. It is used to reprimand statements that may not be completely false, but that hold back some sort of truths. Some players may also choose this option if they believe the person in interrogation is lying, but have no concrete evidence to prove this.
The Doubt option is labeled Bad Cop in the Remastered Edition.
As an interrogation method, doubt is used by Cole Phelps many times to extract truth from eyewitnesses and suspects. While using Truth accepts a given statement and ellaborates on it and using Lie completely denies the whole statement, Doubt is used where the interrogated may be holding back additional information to a varying degree from Phelps.
Doubt should be used when the suspect or witness hesitates on certain details and information before disclosing generalized information, only some of the knowledge, or very little to none. Doubt, if used correctly, will often reveal the information that is being held back. Signs that indicate the need for Doubt include nervousness, shifty glances around the room, avoiding direct eye contact, and unusual body gestures, as well as hesitations on revealing information as previously noted.
Doubt should not be confused with Lies. Where Doubt simply pushes one to reveal the full extent of an event or person, Lies calls a statement into complete question in an attempt to disprove it. As such, use Lies when you believe that what the person is saying is false, and when you have a piece of evidence to contradict what was said, and Doubt when you believe that information is being held back.