No cost-benefit analysis was conducted before the government’s decision to impose body scanning on international passengers departing the country, the government has revealed.

On Sunday Transport Minister Anthony Albanese announced that a $28 million program to install scanners at international airports would proceed after “a successful trial” at Sydney and Melbourne airports. Passengers selected for scanning who refused would not be permitted to fly, the same policy as applies in Britain (in the US, passengers who refuse have the option of a highly invasive pat-down search).

However, when asked what evaluation of the trial had taken place or whether a cost-benefit analysis was conducted by the Office of Transport Security within the Department of Infrastructure, a spokeswoman for the minister advised that “the decision was made based on accuracy and minimising inconvenience to the travelling public”.

The decision to roll out scanners at the nations airports had its origins in the knee-jerk response to the “underwear bomber” Umar Abdulmutallab during Christmas 2009, when his plan to blow up an airliner using a small quantity of liquid high-explosive failed. A later experiment suggested the aircraft would not have crashed even if the terrorist had succeeded in detonating the explosive he had secreted in his underwear.

However, governments across the world immediately rushed to roll out airport scanning technologies claimed to detect liquids, including the Rudd government, which announced it was introducing scanners and allocated money in the 2010 budget.

X-ray-based scanners are now banned in Europe after serious health risks were identified. The scanners used in Australia are millimetre wave scanners that have no known safety issues. The scanners can also be set to not display anatomical features of the scanned individual and not record scans. There have been several instances overseas of scanner operators keeping images of, ogling or commenting on the anatomy of passengers and co-workers.

But the scanners cannot detect liquids secreted within body cavities, are prone to generating false positives, particularly from perspiration, and suffer the same problems of operator error as other forms of scanning equipment: a US Transportation Security Agency official carrying a firearm was able to pass through a scanner at a US airport. They are also supposed to be coupled with a form of profiling to ensure suspicious passengers are more likely to be scanned than the rest of us; anyone who has travelled within the US will know that in fact they’re used by officials if they don’t like your attitude or simply take a dislike to you.

While the government may not have conducted a cost-benefit analysis, two academics, Mark Stewart of the University of Newcastle, and John Mueller of Ohio State, have done so for scanners used in the US.

Readers will recall Stewart and Mueller wrote an extensive analysis of counter-terrorism spending in the US, showing it was wildly in excess of any conceivable cost-benefit analysis. A year ago they looked in-depth at airport scanners, using similar methods to their analysis of war-on-terror spending. They concluded that the scanners would have to stop 1-3 successful attacks a year that would otherwise not have been thwarted by any other security measure. The assessment was based on assuming a catastrophic disaster resulting from a successful attack — assumptions unlikely to be realistic given the limited capacity of even the most powerful liquid explosives and the poor history of previous efforts.

In short, scanners add little to existing security measures and the attacks they are designed to thwart are unlikely to cause major loss of life (such as downing an airliner), thereby significantly reducing their benefit.

There’s a term for this: security theatre, measures that have no security benefit, or the benefits of which are so specific as to be easily avoided by terrorists, but that give people the illusion of safety. In fact there may well be some specific form of psychological impact from scanning equipment that looks high-tech but achieves nothing — recall that hilarious moment during the swine flu beat-up when Nicola Roxon ordered thermal scanners into airports?

But the illusion comes at a cost — a cost to taxpayers, and a cost in delays to airline passengers (recall that far more people died as a result of increased traffic on US roads after 9/11 than died in terrorist acts). The $28 million being wasted by the government on scanners could be redeployed elsewhere within the transport security budget to greater effect, let alone elsewhere in government. Even a relatively small sum would probably save more lives being redirected to health or road safety than it will ever save from terrorists.

So who is the real beneficiary of the government’s decision to impose body-scanning technology on airport users? Tomorrow we’ll look at the giant American defence contractor that will be the only beneficiary of the scanner scam.