[Boudica]

This article provided an interesting perspective on how crimes like the recent Joker attack may reflect more widely on crime, and the taboo of public displays of aggression.
The article starts off by talking about how rare the usual crime you see in other major global cities,  just doesn't exist on the same scale in Japan:

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Japan is an extremely safe country.

I know that's a bit of a cliché. But it's only when you live here that you realise just how different Tokyo is from every other big city on earth.

The sort of petty crime that's common in London or New York, doesn't exist here. Violent crime is something you barely think about - at least as a man.

When a violent attack took place recently on a packed train it set off a lot of alarm bells.

The attach in question is described here. 17 people were injured by a 24 year old man dressed as the Joker. He apparently sprayed some kind of clear liquid around the carriage and set fire to it. He claimed he "worshipped" the Joker character and "wanted to kill as many people as possible". He dressed as the Joker as he claims he looked up to him.

However, psychologists are saying the guy isn't actually a psychopath (in a clinical sense).

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But criminal psychologists say the real point of the costume and the timing was not to mimic, but to draw attention to the outrage he was committing.

"I think he wanted to stand out," says Professor Yasuyuki Deguchi, a criminal psychologist at Tokyo Mirai University.

"He is a distorted attention seeker. By dressing up as the Joker on Halloween night, he thought he will stand out more. By acting like Joker and saying he looked up to him, he can get more attention from the people. I don't think he decided to copy the Joker because he saw the movie."

I've spoken to a number of criminal psychologists since the attack, and they all say the same thing; this was not the crime of a psychopath.

In fact, mass attacks are rarely carried out by people with identifiable mental disorders. Instead, they fit a different pattern. They are overwhelmingly carried out by men who feel rejected by society.

"Social isolation or lack of social bonds is one of the biggest risk factors for criminal offending, like mass killing and other very serious crimes" says Professor Takayuki Harada a criminal psychologist at Tsukuba University.

"So, they have no relatives, no loved ones, no job and no social bonds. They are disappointed by society and very hostile to society. They are also suicidal," he says.