what legal action can be taken against someone who stole another person's identity

Beware of identity theft concerns.

You might find helpful my Legal Guide, "Identity Theft At the Curb"

http://www.avvo.com/legal-guides/ugc/identity-theft-at-the-curb

Contact a local lawyer - many may give you a free consultation for an hour - to discuss your specifics. Far too many variables exist in the short post you wrote for any further observation by me.

In choosing a lawyer, you might find my Legal Guide helpful "How to Choose A Lawyer For You"

http://www.avvo.com/legal-guides/ugc/how-to-choose-a-lawyer-for-you

You might find my Legal Guide helpful " What Do I Tell My Lawyer"

http://www.avvo.com/legal-guides/ugc/what-do-i-tell-my-lawyer

The best way to proceed depends on the answers you provide and many others things.

Good luck to you.

NOTE: This answer is made available by the lawyer for educational purposes only. By using or participating in this site you understand that there is no attorney client privilege between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed professional attorney with whom you have established an attorney client relationship. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific factual or legal circumstance described in the question.