The Huffington Post has come up with a list of tell-tale signs that you can use to identify whether the person you are dating is a sociopath or not.
Sociopath's have an oversized ego, lie on a regular basis, while exhibiting manipulative behavior.
Another red flag for your relationship could be that your partner shows a lack of empathy, remorse or shame and stays eerily calm in scary or dangerous situations.
Behaving irresponsibly or with extreme impulsivity and having just a few friends can be some other traits in sociopaths.
Other things that you should keep in mind while determining if you are dating a sociopath are that such people can be very charming, but only superficially, they disregard societal norms, and have no problem with maintaining uninterrupted "intense" eye contact.