Julian Knight (pictured) has joined a select group: those for whom a state parliament has made a specific law. It is, perhaps, slightly incongruous that some of the key advances in constitutional law have come about thanks to sex offenders, bikie gangs and now possibly a mass murderer.

Last week, Victorian Parliament introduced a law to deny the Hoddle Street murderer any chance of parole, although he will have served his 27-year non-parole period in May. The legal principle at stake is the separation of powers. We have a system that exercises power in a democracy by three separate arms: the legislature, which makes the law, the judiciary, which applies the law, and the Governor-General (advised by the Prime Minister), who leads the public service and governs within the constraints of the law. The Australian constitution makes the separation of powers explicit: see sections 1, 61 and 71. This separation can be considered the backbone of our democratic system.

No doubt the Victorian government had some of the best legal minds beavering away on drafting the legislation, maximising the power to detain Knight and sitting right on the edge of lawfulness. The problem is that this very much looks like judicial power conferred on an executive body, the parole board. Why bother with a criminal trial and judicial sentence if the legislature can simply pass laws to prevent the release of certain prisoners after the fact? What the government is proposing is tantamount to a breach of the double jeopardy principle: revisiting the sentencing process 27 years after Knight was originally sentenced. Such a law begins to look like an attack on the institutional integrity of the courts. Knight has good reason to challenge these laws, and there would be few lawyers who would argue he did not have a shot at succeeding.

Chapter III of the constitution establishes our system of federal courts and grants them — and them alone — the Commonwealth’s judicial power. From time to time, the High Court has been called on to resolve disputes in which the courts’ independent or exclusive exercise of judicial power has been at issue. In lawyers’ shorthand, the cases are called “chapter III” cases.

A central chapter III case, and one Knight (or his lawyers) will be quite familiar with, is that of Kable v NSW DPP (1996). This case concerned a similar situation to Knight’s: Gregory Kable stabbed his wife to death and was found guilty of manslaughter, the charge reduced from murder on the basis of diminished responsibility as a result of Kable’s acute depression. At the end of his minimum four-year sentence, when he was due to become eligible for parole, his plight became a political issue for the NSW government during an election year. To many it looked like political point scoring, but the NSW government would claim that the safety of the populace was the highest law (there is even a Latin phrase for that: salus populi suprema lex). NSW Parliament passed a bill, deceptively titled the Community Protection Act 1994, which allowed preventative detention, but for one man only: Kable.

The legislation was challenged all the way to the High Court, which found it unconstitutional. State courts, in this case the NSW Supreme Court, exercise federal jurisdiction conferred upon them under chapter III, but the High Court found that NSW legislature cannot confer a non-judicial function on the Supreme Court that would undermine public confidence in the judiciary. In other words, the legislature cannot tell a court what to do if, in the words of Justice Michael McHugh, “that might lead an ordinary reasonable member to conclude that the Court was not independent of the executive government of the state”.

“Too often, unpalatable individuals become a foil for such populist shenanigans …”

There have been subsequent similar attempts by legislatures to continue to imprison serious offenders while at the same time skirt around the legal prohibitions established in the Kable case. The most obvious is Fardon v AG (Qld) (2004) — also involving a serious offender — with an act passed in response to Fardon’s imminent release that permitted ongoing detention for the purposes of community safety. In that case, the High Court found procedures in the act of Parliament, such as the onus placed on the Attorney-General to demonstrate the need for ongoing imprisonment of an offender who fell into a certain category, meant the actions of the Queensland legislature came in on the right side of the Kable doctrine.

In these tricky situations, the bar is high: establishing that the institutional integrity of the court has been undermined by an act of the legislature is troublingly difficult. Even the smallest windows of judicial discretion in such legislative attempts to detain prisoners beyond their sentences have satisfied the Kable doctrine. In a subsequent case, Justice Michael Kirby referred to the sad potential for Kable to be “a constitutional guard dog that would bark but once”.

In the case of Julian Knight, we have a bill that names an offender but offers a (albeit narrow) discretion for continuing his detention. The act would require that the Parole Board only make an order for Knight if it is satisfied he is “in imminent danger of dying or is seriously incapacitated” so that “he no longer has the physical capacity to do any harm to any person”. Knight would also have to satisfy the general requirement for parole, namely that he does not pose any risk to the community.

The existence of serious, sometimes repeat criminal offenders coupled with the accepted unreliability of predictions of the danger posed by criminals places the courts at the centre of an intractable problem. The law has traditionally treated personal liberty as a foundation stone of the rule of law; the age-old writ of habeas corpus requires the government to show cause for detention or release (it literally translates to “produce the body”). There are good reasons for this, as power that is not held to account all too quickly becomes arbitrary and concerned only with its own preservation. Too often, unpalatable individuals become a foil for such populist shenanigans, but our whole system of law suffers when political whim takes precedent over the rule of law.

Part of the problem is that the government simply hasn’t allowed the parole process to take its course. On a reasonable reading of the facts, Knight is unlikely to be eligible for parole regardless of whether this particular act is held to be constitutional, as amendments to the system of parole now dictate that protection of the community is the Parole Board’s principal consideration in determining a person’s eligibility. So why go to such lengths to pre-empt the findings of the Parole Board?

Our system strikes a balance between liberty and safety; if we want to reassess that balance, we should do so via calm and considered public debate, not a knee-jerk response in an election year. As Liberty Victoria noted:

“If an exception is made by the government for Knight, then this can easily lead to further exceptions in the future when it is politically expedient. That sets a dangerous precedent.”