Early life Carpenter was born in Louisville, Kentucky and graduated from Sacred Heart Academy in Louisville. She trained at the Walden Theatre Conservatory in Louisville, later the Juilliard School in New York City. Already before graduation she was cast in the Broadway revival of Arthur Miller's The Crucible starring Liam Neeson and Laura Linney.
Career Carpenter first attracted critical attention for her performance in The Exorcism of Emily Rose; she earned the role partially due to her ability to contort her body and face in frightening ways (as Scott Derrickson explains on the DVD commentary, pointing out that most of her "demonic" contortions were achieved without the use of visual effects). She took home the 2006 MTV Movie Award for "Best Frightened Performance", and also received a Hollywood Life Breakthrough Award.
Carpenter currently plays the role of Debra Morgan in the Showtime television series Dexter which premiered 1 October 2006. Her portrayal of the title character's sister has impressed some critics, with Australian journalist Jack Marx describing her "cool and clumsy" performance as "so perfect that many viewers appear to have mistaken the character's flaws for the actor's".
It was widely reported in 2007 that she was dating her Dexter co-star Michael C. Hall. They announced in early January 2009 that they had eloped on New Year's Eve in California .