Batman was the first superhero in comic book history without superpowers. Although he could solve some problems with technology, there were still problems he could not solve.
He first appeared in 1939. That same year, a case occurred in America. The police had illegally wiretapped the defendant's phone and used the recordings as the primary evidence to accuse Nardone of illegal business operations, but the Supreme Court ruled that not only could such wiretaps not be used as evidence, but clues obtained from the intercepted calls could not be used as evidence either.
This principle later became known as the "Fruit of the Poisonous Tree." It originated with the 1920 Silverthorne Lumber Company lawsuit. Just as a tree was "tainted," the fruit it bore could not be used as evidence. Even if Batman caught a criminal, if the evidence had been obtained illegally, the criminal would still be acquitted under the Fruit of the Poisonous Tree doctrine.
Every cause had an effect. The reason Gotham had so many Joker followers was also tied to Wayne Enterprises. Since Bruce Wayne could not run the family business himself, Wayne Enterprises had fallen under the control of CEO Earl and become a profit-driven conglomerate.
The Joker used money stolen from banks as prize money for a "parade celebration," luring people to join his "party" and hunt Batman.
Batman hunted the Joker, but even if a madman like the Joker was caught, he would be placed in a psychiatric hospital according to the law. Once he regained his freedom, he would trigger another crisis.
But the moment Batman decided not to execute the Joker through vigilante justice, if he wanted to bring a criminal to justice, he had to follow legal procedure. The Joker wanted to lure Batman into killing him. That would not