If you are in tune with your chakra energies, you will feel a "gut check" between the solar plexus and the sacral chakra when someone is lying (the area I am speaking about is around the navel both an inch above and below. That area should tighten in response to a lie). But again, you must be in tune with your major chakras. For more information on that, check out my hubs on Chakras.
We are all empathic to some degree but a true empath who uses their gifts to help and serve others needs to become as spiritually awakened as possible. Not knowing your personal circumstances I can only recommend that you take time to study chakras, energy, meditation and other spiritual tools. A great book to help someone on a spiritual path understand more about energy and empathic reception is The Celestine Prophecy by James Redfield. It is written in novel format but is filled with spiritual insights.