Answer:
While 'sociopath' is generally not considered a clinical term, it is often what the public calls someone with Antisocial Personality Disorder.
Antisocial Personality Disorder is a mental disorder listed in Axis II of the DSM-IV. It requires someone to show a disregard for the rights of others (both legal and 'inborn') since age fifteen, with evidence of this before age fifteen as well (often evident in juvenille criminal behavior).
So, generally speaking, no. It has to have been evident since teenagehood.