Before she came to prominence as a no-nonsense assistant district attorney on the TV crime series Law & Order, this beauty first launched a career in her native Canada. A burgeoning interest in music led to a part in the musical Buddy, and she subsequently relocated to New York. In 1993, she put her music on hold when she landed her pivotal role on Law & Order and left after three years to pursue other opportunities. For the rest of the decade, she played supporting parts in a number of independent films before returning to series television in 2001 as a medical examiner on Crossing Jordan. The series concluded in 2007, and since then she's pursued television and film roles while focusing on her music career and raising a family.
- Speaks Italian, French, Spanish and German.
- Song "The Ballad of Jill Hennessy" by Mollycuddle was written about her.
- Used to play guitar and sing in the New York subway for money.
- In 1988's Dead Ringers, her first movie role, Hennessy and her twin sister, Jacqueline Hennessy, played twin prostitutes.
- Made her Broadway debut in the Buddy Holly musical Buddy in 1990.
- Opened Hennessy's Tavern in Northvale, NJ, in 1999.
- Performed Bob Dylan's "It's All Over Now, Baby Blue" and Tom Waits' "You're Innocent When You Dream" on the 2003 Crossing Jordan soundtrack.
- Released debut album, Ghost in My Head, in 2009.
- 1995, Screen Actors Guild Awards — Outstanding Performance by an Ensemble in a Drama Series: Nominee
- 1996, Screen Actors Guild Awards — Outstanding Performance by an Ensemble in a Drama Series: Nominee
- 1994, Screen Actors Guild Awards — Outstanding Performance by an Ensemble in a Drama Series: Nominee
- Jacqueline Hennessy — Sister
- John Hennessy — Father
- Eleanor Hennessy — Grandmother
- John Paul Hennessy — Brother
- Marco Mastropietro — Son
- Paolo Mastropietro — Husband
- Maxine Hennessy — Mother
- Gianni Mastropietro — Son