Sylar's lie is easily detected by Sue Landers' Claircognizance.
Claircognizance is an ability similar to the classical idea of "extra sensory perception," in which a person constantly receives little "packets" of information about their surroundings a normal person would not be able to have. Some powerful telepaths are able to draw on this ability to gain information about their surroundings without use of any of their five senses. This ability is generally passive, though sometimes a person could concentrate on what they wanted to receive information about. People may have this ability without realizing it, as it can be mistaken for strong powers of observation. However, the power differs from strong powers of observation in that it allows the user to instantly know concrete facts without having to go through the mental process of deduction.
A more powerful form of this ability simply grants the user complete knowledge of a certain subject, without having to study. It is simply a matter of remembering the information the ability gives access to.