Janet Van Dorn became Gotham City's district attorney after Harvey Dent's mental breakdown.
When Police Commissioner James Gordon was accused of accepting bribes from Rupert Thorne, Van Dorn reluctantly told Barbara Gordon that the evidence was solid enough to keep her from dropping the charges or allowing Gordon bail. Gordon was eventually cleared, as the crime was shown to be a frame-up by Deputy Commissioner Gil Mason.
Unlike Gordon, Van Dorn deeply resented Batman's interference in law enforcement, which created a bizarre collection of costumed criminals who were difficult to prosecute. As such, she made no secret of her contempt for the superhero and vowed to prosecute him when possible (Ironically, she at one time seemed to be in a romantic with Batman's alter ego, Bruce Wayne).
However, this changed when Van Dorn was abducted by the inmates of Arkham Asylum and held at the mental hospital. Shortly thereafter, Batman was captured as well for the purposes of a twisted trial that indicted the Dark Knight for making them insane costumed criminals. To her surprise, Van Dorn was forced to defend Batman, on the threat that she would be murdered along with him if he was "convicted." Although Van Dorn was naturally unenthused at this situation, Batman convinced her to play along.
The trial seemed hopeless from the onset with Two-Face conducting the prosecution, Joker being the judge and a grotesquely biased jury made up in part of Harley Quinn, The Mad Hatter, The Riddler and Killer Croc, all determined to kill Batman at this farce's conclusion. However, Van Dorn cunningly blindsided each witness to confess that, while Batman may have been a stylistic influence, they themselves were solely responsible for becoming violent criminals.
To Van Dorn's surprise, the jury formally acquitted Batman, but Joker cheerfully announced they were going to kill Batman and his advocate anyway. Fortunately, at the moment of Batman's unmasking in the electroshock therapy room, Van Dorn realized she had a batarang from an earlier encounter with the Dark Knight and uses it to smash the room's only light. Batman took advantage of the situation to immediately escape his straitjacket and fight back.
Eventually, Batman and Van Dorn escaped and defeated the Joker while the Gotham Police Department arrived to subdue the prisoners.
Afterward, Van Dorn respectfully reconciled with Batman and his useful role in the city, but vowed to work to change the city to make him unnecessary. Batman respectfully vowed to do the same.
Van Dorn was a lawyer of superb skill who could acquit a client even in an impossibly prejudiced court. Part of that ability came from her brilliance in questioning witnesses, such as when she goaded Poison Ivy to reveal her insanity by plucking the petals of a flower, knowing full well it would drive Ivy berserk.
Background Information Edit
For her major appearance, in "Trial," Janet Van Dorn is voiced by Stephanie Zimbalist - the daughter of Efrem Zimbalist, Jr. (the voice of Alfred Pennyworth), and also a former classmate of Kevin Conroy's from Julliard.