Lie is the third interrogational accusation option that the player has access to in L.A. Noire. It is used when the suspect is lying and the player has concrete proof.
As with Doubt, suspects who are lying will have shifty eyes, possibly a smirk, or will be scoffing or laughing. Some more adept liars may show much more subtle signs, such as quick eye twitches or fidgeting.
The Lie option is not to be confused with Doubt - in order to use this option correctly, the player must have concrete evidence that the suspect is lying.
For example, if someone claims they did not kill their husband and you do not have any evidence linking them, you Doubt them. If you have the murder weapon and their bloody clothes as notebook evidence, you can select Lie and use these as substantial proof.