Judge Doom is the much-feared Judge of Toontown. Despite presiding over a city of Toons, Doom is totally without mirth and passes capital punishment on Toons who break the law, placing them in a chemical vat of turpentine, acetone and benzene (essentially oil, paint thinner, and film dissolver) which he dubs "The Dip". This concoction will dissolve Toons, permanently killing them. He wears gloves supposedly to avoid the mess (but as it is soon revealed, it is actually to prevent himself from being dissolved). The Judge employs Toon henchmen (the "Toon Patrol") to assist him in hunting down Roger for the murder of Marvin Acme, which he framed for the act he did himself.
Judge Doom displayed two very different personalities in the film, both equally menacing to his enemies.
Judge Doom is a calm and reserved man without mercy and brutally executes those who perceives as guilty or stand in his way. He has an ambition to erase Toon Town in order to create a freeway due to its profit and potential benefits;buying then dismantling the "red car" to avoid competition and taking money from his theft at the bank to launch the project. Judge Doom also possess cunning as he lures out Roger Rabbit with the "Shave and a Haircut" trick. He had a Hitler complex which he tries to deny to the extent of disguising himself as a human to try to rid the world of Toons, despite being one himself. However when he was being run over, he acts like a Toon (screaming incomprehensible noises in fear) and does not deny it once the jig was up, but "not just any Toon"...
After Judge Doom re-inflates himself and reveals himself as Teddy's killer with reunion with Eddie he tells him why he should not remember his eyes, but his voice (which grows higher until it reaches a horrifyingly high pitch) and his eyes turn to daggers ready to kill him. Though he doesn't talk again until his demise, he pursues Eddie when he was running away, turns on the cannon to melt Roger and Jessica once he was pushed to the ground, punching Eddie with an anvil, turning it into an buzz saw to demonstrate how lethal it was and the swirling eyes with a wide grin as he was gradually getting closer to kill Eddie. All these traits show he was a deranged and sadistic psychopath who enjoys making his victims watch as their friends die and loves to kill them slowly in the most agonizing way. He does have fear of death, as he instantly panicked as soon as the Dip hit him and screamed as he dissolved.
When the film first introduces Judge Doom, Lt. Santino confides to Eddie Valiant that Doom bought the election. Later, at the Terminal Bar, Doom uses the "Shave and a Haircut" trick to lure Roger out, then prepares to execute him. After a brief scuffle inside the bar, the Judge orders the weasels to capture Roger and Eddie Valiant. Roger realizes he's in trouble with Doom after him and begs Eddie to hide him. When Eddie learns that studio head R.K. Maroon is connected to the plot to frame Roger, Eddie interrogates him, but Maroon pleads that he is "a dead man" if he confesses. Just as Maroon is about to spill everything, he is killed by an unseen gunman who nearly shoots Eddie as well.
Upon chasing the killer to Toontown, Eddie catches Jessica Rabbit, thinking she's the murderer, but Jessica reveals that Judge Doom was the one who killed Acme and Maroon. At the film's climax, Doom traps Eddie, Jessica and Roger in the Acme Factory to explain his scheme: Erase Toontown from the map using a giant, mobile vat of dip linked to a high-pressure water cannon and then build a freeway over it. Doom then plans to retire from being a judge and control all the profits from the new road system. Doom also reveals that he is the sole stockholder of Cloverleaf Industries and explains that he bought the "red car" (the Pacific Electric Railway) for the sole purpose of putting it out of commission. He then orders Jessica and Roger Rabbit to be tied up and raised into the air via skyhook to be sprayed by the dip cannon.
Valiant distracts the weasels using hilarious antics (partly while singing The Merry-Go-Round Broke Down to the accompaniment of an orchestrion-like instrument playing the tune) to make them literally laugh themselves to death, then attempts to rescue Roger and Jessica when he is interrupted by Doom. The two men then square off, dueling with various ACME props. During the fight, Judge Doom is run over by a steamroller, but does not die as expected. As the steamroller crushes him, Doom's body is flattened into a flimsy paper-thin shape, revealing himself to be a Toon wearing an assortment of fake, but live, props, such as fake eyeballs, false teeth and a rubber mask in order to disguise his Toon body. After he re-inflates with an oxygen tank, he shows his red toon eyes and talks in a high squeaky voice and Eddie recognizes Doom as the bank robber in Toontown long ago who murdered his brother, Teddy Valiant, thus triggering his hatred towards Toons and explaining how Doom managed to buy the judicial election and the trolley car company.
Being a Toon, Doom turns out to be capable of sprouting an anvil and an extendable buzzsaw from his hand, with which he attempts to kill Eddie. In the end, Eddie proves to be too clever, using his own dip concoction to dissolve him, leaving behind his human disguise. Doom melts and burns away screaming before he dies. A crowd of various Toons then surround his burned empty suit and melted face and wonder what kind of Toon he was. It hasn't been revealed what type of Toon he was, or if he was one specific type of Toon at all, but the Toons seem to agree that they don't need to know, and decide to live happily ever after when the will of Marvin Acme suddenly appears in Roger's possession, granting full ownership to the citizens of Toontown.
The Resurrection of Doom
In the graphic novel Roger Rabbit: The Resurrection of Doom, it is explained that Doom was originally a Toon named Baron von Rotten, who took up the role of playing the antagonist in movies, until an accident in which Von Rotten suffers a concussion, and awakens believing he is a real villain. Von Rotten thus begins his crime career, robbing the First National Bank of Toontown, then killing Theodore 'Teddy' Valiant by dropping a piano on his head, and spreading the stolen money all over the town in order to buy the election for Judge of Toontown, assuming the new name of Judge Doom.
He was revived by another gang of weasels who, using an old cel and a multiplane camera, were able to revive him, proving it is possible to revive a toon. Doom disguises himself as a director, forcing Roger to purposely tone down his acting, in hopes to ruin his career, and has other designs in mind for his revenge.
Powers and abilities
In his flesh-and-blood guise, Doom uses his skull-headed swordstick and ACME products to fight Valiant. While in his Toon form, he has evil red eyes and a squeaky voice, and is able to produce an arsenal of tools from his body which he can employ as weapons, including a buzzsaw and an anvil. He uses springs in his feet to jump far distances, and (like most Toons) can survive anything but his own dip, which dissolves him to his death.
- One of the early drafts of the script was going to have Judge Doom be revealed as the hunter who killed Bambi's mother but was changed for unknown reasons. 
- Doom appears to bear some resemblance to Roland Freisler, the notorious Nazi figure who was also a ruthless judge.
- Doom's death is a reference to the Wicked Witch of the West's death in The Wizard of Oz, and they both melt and shout "I'm melting!"
- The Nostalgia Chick, of thatguywiththeglasses.com, listed Judge Doom as #7 on her "Top 10 Evil Nostalgia Characters" list.