Born in Dallas, TX, Mitchell knew at a young age that she was going to become an actress. She landed her first role at seven years old when she appeared at the Dallas Theater Center in "Alice in the Looking Glass." Later in life, she attended Booker T. Washington High School for the Performing and Visual Arts, an arts magnet school in Dallas. She graduated in 1988 and moved on to Stephens College in Columbia, MO to continue studying her craft. Though she wanted a stage career in her hometown, Mitchell instead began performing in regional and summer stock theater in Missouri and Iowa. She later crossed the pond to study Shakespeare at the British American Drama Academy in London, an acting school composed of students from around the world who study with some of Britain's more accomplished thespians. For her part, Mitchell excelled as Rosaline in the Bard's comedy "As You Like It."Returning to the states, Mitchell landed her first regular television role, playing Dinah-Lee Mayberry on the now-defunct daytime soap "Loving" (ABC, 1982-1996). Because of her Shakespearean training, Mitchell took her role very seriously, forcing a frustrated group of writers and producers to constantly make script changes. She was fired after four months. Mitchell went back to the stage as an understudy in Edward Albee's off-Broadway production, "Three Tall Women," and soon appeared again on television in an episode of "The Sentinel" (UPN, 1995-99) before landing a regular role on the short-lived drama, "L.A. Firefighters" (FOX, 1996). Mitchell played the unhappy wife of a charismatic fire captain (Jarrod Emick) whose commitment to his work has earned his crew's respect, but harmed his marriage. But after only seven aired episodes, "L.A. Firefighters" was cancelled. The actress bounced back with an episode of the popular "JAG" (NBC, 1996-2005), playing a fighter pilot facing court martial after being accused of fraternizing with a married enlisted man.In 1998, Mitchell landed her breakthrough role with her strong performance in "Gia," playing the on-again-off-again lesbian lover of Gia Carangi (Angelina Jolie), one of the first supermodels whose fame and celebrity led to a life of wanton hedonism and ultimately a tragic death from AIDS in 1986. Mitchell's performance marked her first film role - and her first onscreen nudity, including an extended love scene with Jolie, which the inexperienced actress handled with utmost professionalism. Meanwhile, she returned to regular television work with the short-lived drama, "Significant Others" (Fox, 1997-98), followed by a supporting role in her first theatrically released film, "Molly" (1999). After an episode of the "Party of Five" spin-off, "The Time of Your Life" (Fox, 1999-2000), Mitchell starred as former Rolling Stone photographer Linda Eastman who went on assignment to photograph The Beatles and eventually married Paul McCartney (Gary Bakewell) in the made-for-television movie, "The Linda McCartney Story" (CBS, 2000). Back on series television, she followed with a recurring role on "ER" (NBC, 1994-2009), playing a lesbian psychiatrist with more than a passing interest in Dr. Kerry Weaver (Laura Innes). Back in the feature world, Mitchell landed supporting roles in "Nurse Betty" (2000) and "Frequency" (2000) before returning to the comfortable confines of television with an episode of "Spin City" (ABC, 1996-2002). She next starred opposite lesser-Baldwin brother, William, in HBO's "Double Bang" (2001), a crime thriller about a cop trying to avenge his partner's murder. Mitchell followed with yet another short-lived regular series stint, this time on "The Beast" (ABC, 2000-01), a one-hour drama set in the world of a fictional 24-hour news station. If "Gia" helped boost her profile to people in the entertainment industry, her next role, playing Mrs. Claus in "The Santa Clause 2" (2002), helped make her a recognized public face, giving the actress plenty of opportunity to explore more high-profile parts.While film may have provided the means for Mitchell to become more widely known, she continued to be a steady presence on the tube, including appearances on episodes of "Law & Order: Special Victims Unit" (NBC, 1999-) and "CSI: Crime Scene Investigation" (CBS, 2000-15). But her misfortune in choosing long-term ratings winners continued when she was hired as a regular on "Lyon's Den" (NBC, 2003-04), a drama set in a law firm that dealt with the relationships between the clerks and the partners. The show, which the network had high hopes for since it starred ex-"West Wing" star Rob Lowe, was scraped after NBC aired just the pilot episode. She did, however, land meatier guest parts on well-established shows, including "Boston Legal" (ABC, 2004-08), "Everwood" (The WB, 2002-06) and "House" (Fox, 2004-12). On the latter, Mitchell was a nun who thinks the red boils on her hands are actually stigmata until House (Hugh Laurie) discovers an allergy to copper triggered by an IUD lodged inside the good sister's uterus made of the material in question.After a minor part in "Running Scared" (2006), a little-seen action thriller starring Paul Walker as a low-level mafia thug trying to track down a gun used to kill a cop, Mitchell landed another breakthrough role on the TV phenomenon, "Lost" (ABC, 2004-10). Playing one of the mysterious Others whose seeming compassion towards a captive Jack (Matthew Fox) possibly masked a more pernicious and conflicted nature, Mitchell established herself as a significant presence at the beginning of season three, which carried on throughout the next two, as her character of Dr. Juliet Burke slowly became a trusted ally while becoming romantically involved with Jack and Sawyer (Josh Holloway). Meanwhile, she revived her role as Mrs. Claus for the third installment to the holiday franchise, "The Santa Clause 3: The Escape Clause" (2006), while leaving "Lost" prior to the show's final season to join the cast of "V" (ABC, 2009-11), a retelling of the classic 1980s miniseries about human-eating aliens taking over the Earth. She did, however, return to "Lost" for the first episode of the last season, in which she gave a tearful goodbye to Sawyer after helping to explode a bomb that reverses time travel on the island. Her character also appeared in a few scenes over the show's final episodes, earning her an Emmy Award nomination for Outstanding Guest Actress in a Drama Series.