Suicide is still against the law in many countries. How did it come to be considered a crime in the first place? 

That old joke about imposing the death penalty on people who try to kill themselves but fail?

It was reported in June that more than 100 male detainees had made suicide attempts on Manus Island in recent months, with the incidence spiking horrendously after the federal election. Among them, a 30-year-old man had set fire to himself and his "room" (a converted shipping container). He survived, but Papua New Guinea police announced that he would be charged with the crime of attempted suicide. For that, he could face a prison sentence of up to one year. It took me back to law school and the bemusement in the lecture theatre when we learned that the state of NSW had only recently (in 1983) amended its Crimes Act to abolish the crimes of suicide and attempted suicide. Yes, indeed. At common law, if you tried to kill yourself, or actually did take your own life, it was a crime.

The present fact is that about half the countries in the world no longer treat suicide as a crime, but the other half still do. In most, it isn't enforced in practice (rather like that other NSW-specific holdout, abortion), but there are still a few places that treat it with deadly seriousness.

Malaysia quite commonly prosecutes attempted suicides, usually resulting in sentences of up to six months' jail. Singapore was similar but has just passed a law to repeal the crime. Saudi Arabia also tends to the severe: last year, a man was given a month in jail and 60 lashes just for threatening to kill himself. It seems that a lot of African countries also still punish attempts.

In Western countries, it's a historical anomaly, although some US states that recognise common law crimes still have it on their books. The UK abolished it in 1961.

Where did the crime come from in the first place? It seems that we can blame St Thomas Aquinas for its philosophical root, although there's a more mercenary angle too. Aquinas reasoned that suicide had to be unlawful since it conflicts with man's natural inclination to love one's self, at the same time impinging upon "the province of God". From a theological perspective, that makes sense, since having a general licence to smite ourselves would rather upset the divine order of things.

Much of the criminal law did and still does have a strongly religious basis, whether we see the ethical rules of communal behaviour (you know, the commandments) as being the word of God or as a logical expression of the values we'd have developed even without religion to enable us to get along. However that is, it's unremarkable to find the rule against suicide coming from a starting point of belief about right and wrong.

The competing theory is that suicide became a crime in a rather backward way. Back in 967, King Edgar of England made a law that said the property of someone who had died by suicide would be forfeited to his feudal lord. Forfeiture was, in medieval times, a common penalty for felonies. The logic goes that, because the king had decided to add suicide to the list of acts that would cause forfeiture, it came to be assumed that it must be a crime too.

As the law developed, attempted suicide fell into the class of low-grade crimes called misdemeanours, usually punished by a fine or short jail term. Actual suicide became a far more serious thing: a felony. Suicides were punished by forfeiture of their entire estate to the king (a huge deal back in the day, when inheritance of land and title was society's glue) and "ignominious burial on the highway".

Really it was a delayed manifestation of Enlightenment thinking that brought the crime of suicide into disrepute, then ridicule and eventual repeal. In a world governed by the twin pillars of church and crown, the idea that a person might have ownership over their own body (and, by extension, life) was a bit exotic. The Enlightenment, critically, broke away with the thought that our choices, if not necessarily our destiny, might be our own to make. Once that got started, while it could continue to be believed on ethical grounds that ending one's own life by choice should be discouraged (whether because it's a sin or for non-religious reasons), it was going to be difficult to maintain it as a secular crime.

The demise of enthusiasm for punishing self-harm might be thought a historical curiosity if you live in Australia, until you remember that the distinction between suicide per se and voluntary euthanasia is only one of logistics.

While the euthanasia debate will be fought out for a while to come, I think we can detect its ultimate conclusion in the story of how suicide by one's own hand came to be seen as a tragic, but not criminal, act. The battles between personal rights and social norms play out over centuries, not years.