But that’s only part of the equation. The criminal law is based on the idea that to be punished, an accused person must not only do the act but also have the intention to do what they did. This is not a modern principle founded in political correctness. It’s one of the bedrocks of our laws going back centuries.

With an election around the corner, Premier Daniel Andrews, clearly not wanting to appear soft on law and order, has promised that people who injure Victorian emergency service workers even during a psychotic episode will be sent to jail. The government plans to introduce the laws in the second sitting week of June.

Last week there was outrage at a decision by County Court Judge Barbara Cotterell, who cited “special reasons” for not sending Amanda Warren and Caris Underwood to jail for assaulting a paramedic in March 2016 in Reservoir while under the influence of alcohol and cannabis.

So if, like McNaughten, you have such mental health problems that you can prove that you don’t know what you’re doing is wrong, or don’t know what you’re doing at all, then you cannot be held criminally responsible for your actions.

The defence is usually only available for very serious crimes - not common assault. And people who are found not guilty by reason of insanity or unable to stand trial because they do not comprehend the charges brought against them do not get off scot-free. They usually spend many decades locked up in a psychiatric facility.

Judge Cotterell did not have to deal with such difficult issues. But she did have to weigh many complex and conflicting matters before arriving at a sentence. So she had to look not only at the terrible crime but also at the women who had made “enormous” efforts to turn their lives around after “appalling” childhoods and battles with drug, alcohol and mental-health problems.

The truth is that judges agonise over every sentence they hand down. That’s because every crime must be punished and yet every criminal has their own story to tell.

Unlike people on talkback radio, judges must consider not just the objective facts of the crime, but also deal with the person who stands before them and over whom they have the power to lock away for years or decades. It’s an ominous responsibility.