Absolutely nothing is known about Carroll, other than she got a job as a coroner in Santa Monica, California. She has shown members of the BAU the bodies of victims whenever they investigate cases in Los Angeles County.
Carroll shows Prentiss and Reid the bodies of Chase Whitaker's first four victims, saying that all of the victims were drowned but that the first victim, Jake Shepherd, was fatally strangled before being submerged. She then tells them about the broken ribs and sternum damage she found, which indicated severe chest compression, but there were no signs of external trauma. This meant that the unsub was killing his victims and then resuscitating them. Reid compares this to what Rodney Alcala would do to his victims, then asks Carroll if the victims were resuscitated more than once. She replies that it is possible, then checks the X-ray photos of the victims' lungs. She immediately tells them that Shepherd was the only victim who wasn't resuscitated more than once, since the strangulation damaged his throat to the point where water couldn't be expelled from the lungs through CPR.
Later, after Chase kills a woman, Carroll shows Prentiss and Reid the victim's body. She also tells them that the body wasn't moved post-mortem, unlike the other victims. The two agents find a lot of post-mortem wounds, including defensive wounds, on the victim, which indicated the unsub is unraveling, having performed overkill on the woman, and the victim fought back before dying. Carroll then informs them about blood found the body that didn't belong to the victim, which had a severely low white blood cell count. Reid comments that the unsub is literally sick and getting weaker, explaining why he wasn't weighing his latest victims down in bodies of water. When Prentiss explains that the repeated drowning and resuscitation is extremely important to the unsub, Carroll replies that the killer may not be too happy at the moment, since she found that the latest victim was drowned once and unsuccessfully revived.
Carroll shows Reid and Blake the body of Lindsay Leeman, and tells them that she and Chad Mills's other victims died from being stabbed and that her body was burned post-mortem. The two agents assume that the burning is a forensic countermeasure that eliminates trace evidence and makes body identification and determination of a common victimology difficult. Later, after a fourth victim is found, Carroll shows Reid and Blake his body and tells them that he was fatally drowned in bleach.
- Carroll is the third of nine characters in a medical profession to appear more than once in the show's history. The others are:
- Doctor Sherman, who appeared in the Season Six episodes Valhalla and Supply and Demand.
- Doctor Ray Mathis, who appeared in the Season Six episode The Stranger, then reappeared in the Season Eight episode The Pact.
- Doctor Tony Wilson, who appeared in the Season Two episode The Big Game, then reappeared in the Season Ten episode The Itch.
- Doctor Weiss, who appeared in the Season Eight episode The Replicator, then reappeared in the Season Ten episodes Fate, Nelson's Sparrow, and The Hunt.
- Doctor Pat Lewis, who appeared in the Season Nine episode The Inspiration, then reappeared in the Season Eleven episode Awake.
- Doctor Samuel Bayo, who appeared in the Season Six episode Sense Memory, then reappeared in the Season Eleven episode A Badge and a Gun.
- M.E. Cranston, who appeared in the Season Seven episode There's No Place Like Home, then reappeared in the Season Eleven episode The Sandman.
- Doctor Taylor, who appeared in the Season Nine episode The Return, then reappeared in the Season Thirteen episode The Dance of Love.