The sword pictured in an evidence bag being removed from a Marsfield home as part of last month’s anti-terrorism raids was plastic. It is decorative, not deadly.

The reaction on social media has been one of bemusement. The assumption, which I suspect is true, is that the sword was taken in error. But Australian law is broad enough to potentially criminalise the possession of a plastic sword.

There are at least two relevant provisions.

S. 101.2 concerns providing or receiving training connected with terrorist acts. Under subsection (1), a person commits an offence if:

(a) the person provides or receives training; and (b) the training is connected with preparation for, the engagement of a person in, or assistance in a terrorist act; and (c) the person mentioned in paragraph (a) knows of the connection described in paragraph (b). Penalty: Imprisonment for 25 years.

Could a plastic sword be useful in the process of training someone in preparation for the engagement of a terrorist act? To secure a conviction, the possession of the plastic sword would be insufficient. The prosecution would need to demonstrate that someone was providing or receiving training. The sword on its own would not be enough.

But s.101.2 is not the end of the matter. Under s.101.4 (1) of the Criminal Code, a person commits an offence if:

(a) the person possesses a thing; and (b) the thing is connected with preparation for, the engagement of a person in, or assistance in a terrorist act; and (c) the person mentioned in paragraph (a) knows of the connection described in paragraph (b). Penalty: Imprisonment for 15 years.

If it could be demonstrated in a court of law that a plastic sword was connected with preparation for the engagement of a person in a terrorist act then possession of that sword – plastic or otherwise – would be enough to secure a 15 year sentence.

The detail of the offence is worth thinking about: preparation for engagement – not actual engagement. But what constitutes preparation for a terrorist act?

Lots of things are potentially useful to terrorists. Maps of the national electricity network (see the 2006 case of Faheem Khalid Lodhi); a Toyota Hilux (insurgents everywhere); a SIM card (see the case of Mohamed Haneef). By making it an offence to prepare for a terrorist act, we are forced to ask when does such preparation begin. Does the would-be-terrorist need to park the van in Times Square, New York? Should we intervene earlier when they take active steps to implement their plans by downloading a map? Perhaps we should act when the suspects chat online? Where is the line between playing at jihad and being an actual terrorist?

I don’t envy ASIO and the intelligence community. But I am uneasy with preparatory offences – pre-emption and prevention do not sit easily within the criminal law. Traditionally, that body of law demands evidence beyond all reasonable doubt.

With preparatory offences, the integrity of the criminal justice system relies on the prosecution not pursuing a case constructed around flimsy (plastic?) evidence. Or we rely on a jury to refuse to convict. And in the current context we must ask: if possessing a “thing” is already an offence under the Australian Criminal Code, do we really need not just one but three new tranches of anti-terror laws?

It may be amusing that a plastic sword was carted away in an evidence bag – but the truly alarming thing is that possession of a plastic sword has the potential to attract a 15 year jail sentence.