Hadden Irving Clark serial killer suspected of murders in several states. Hadden is known to use many female aliases but his most well known is Kristen. 

This letter is signed by Kristen, not one of the other female monikers he's known to use. 
Four page handwritten letter dated January 22, 2006 and hand signed, Love, Kristen. 
Includes the original prison stamped mailing envelope postmarked Jan 23 2006 and hand signed, Clark.

Hadden Clark Letter Signed Kristen and Envelope Set