"Batman! I accuse you of interfering with the right of criminals to commit crimes!"
-- Batman #163, "The Joker Jury"
During the 1940s and 50s, comic books featuring horror and criminal themes were among the most popular titles being published. Believing that these books were helping to fan the flames of juvenile delinquency in young men, Dr. Frederick Wertham published "Seduction of the Innocent: The Influence of Comic Books On Today's Youth" in 1954. In his book, Wertham reprinted gruesome, violent and sexually thematic images from popular comics. He argued that comics encouraged anti-social and homoerotic behavior in American youth.
The public responded with disdain towards the comic industry. Many forbade their children from reading the books. In order to stay in business and win back the trust of the general public, the major comic publishers created the Comics Code Authority and began self-regulating the content of their books. Comic-book publishers had to abandon the zombie-, monster- and crime-themed books that were their chief moneymakers in favor of less-popular comedic and toned-down books. Many publishers had to close their doors. If not for the successful revival of superhero comics by Marvel and DC in the 1960s, the comic book might have vanished altogether.
As a result of pressure from comic-fearing parents and the creation of the Comics Code Authority, the Joker was portrayed as a more comedic figure during the 1940s and 50s. His tone was shifted from that of a crafty, dangerous murderer to a wacky, annoying prankster. He became a mischievous thief who concocted elaborate heists that often involved intricate puzzles and disguises.
While the Joker now practiced a more non-lethal array of activities, he remained one of Batman's most intelligent adversaries. He employed numerous gimmicks such as "Crime Costumes," Joker utility belts and even a Joker-Mobile that featured a large Joker face on the front grill to help further his criminal schemes. This version of the villain lasted until the 1960s. Then, Julius Schwartz, who was not a fan of the Joker character, started editing the Batman comics. The Joker nearly disappeared into comic-book oblivion.