A study by Mahmut & Stevenson (2012) has found impaired senses of smell in people with sociopathic tendencies.
The study sample consisted of 79 subjects, and the sample was taken from the community (as opposed to a psychiatric clinic).
Researchers found that people that scored highly on sociopathic traits had more difficulty identifying scents and differentiating between scents.
The researchers hypothesize that not only may sociopathic behavior be connected to frontal brain impairment, but there may also be impairment in other olfactory areas of the brain. The amygdala is one of the parts of the brain that process olfactory sensations, or smells. The amgydala is also connected to social interaction and aggression, two traits that may be found in people with sociopathic behavior.
The study authors stated that it would be more difficult to "fake good" or "fake bad" on an olfactory test.
Obviously there need to be more studies with a higher sample size in order to make further connections between sociopathic behavior and sense of smell.
Read the Science Daily article about this study: http://www.sciencedaily.com/releases/2012/09/120920115739.htm