Most drivers assume that once police clock you on a LIDAR speed gun, the reading is unchallengeable. Case law says otherwise — and it’s a defence that’s still relevant today.
In a series of South Australian Supreme Court decisions, courts examined how police prove that a handheld LIDAR speed gun was actually accurate at the time a driver was detected speeding. The outcome surprised a lot of people: several speeding charges were dismissed — not because the devices were found to be faulty, but because the prosecution couldn’t adequately prove they were working correctly on the day.
That matters, because in a criminal or quasi-criminal prosecution, the burden is on the prosecution to prove every element of the offence beyond reasonable doubt — including that the device recording your speed was reliable.
How LIDAR devices are supposed to be tested
Handheld LIDAR speed guns go through two layers of testing:
- Annual calibration — under Australian Standards, this confirms the device is accurate to within a margin of error of roughly +2/-3 km/h.
- A “five-step test” — conducted by the operating officer before and after every shift, to confirm the unit is still functioning correctly.
Once the shift testing is done, a senior officer typically signs a Certificate of Accuracy, and it’s this certificate that police rely on in court to establish the device was accurate when your alleged offence occurred.
Why the certificate isn’t always enough
The Supreme Court found that a Certificate of Accuracy can be challenged — including by evidence given by the very officer who signed it. Where that evidence doesn’t properly establish that the five-step testing was carried out and passed, the prosecution can lose the ability to rely on the certificate at all. Without it, they may not be able to prove the device was accurate — and without that, they may not be able to prove the speeding charge.
Importantly, none of this means the courts have found LIDAR guns to be inherently unreliable. The issue is narrower and more technical: whether the paperwork and testing evidence actually proves accuracy on the day, not whether the technology works in principle.
What this means if you’ve been fined or charged
If you’ve received a speeding infringement notice or been charged with a speeding offence based on a LIDAR reading, this line of case law opens up a genuine avenue to challenge it — but it’s a technical, evidence-based argument, not something to run without proper advice. It typically requires:
- Obtaining the calibration and testing records for the specific device used
- Scrutinising the Certificate of Accuracy for gaps
- Potentially cross-examining the officer who signed it Every case turns on its own facts, and testing procedures and case law in this area continue to evolve
Speak to a traffic and criminal law specialist
If you’re facing a speeding charge or want to know whether an expiation notice can be challenged, get advice before you plead. Contact Harvard Defence Lawyers —Australia’s fixed-fee criminal defence specialists, available 24/7, with offices in the Merrylands, CBD, Blacktown, and Belmore within NSW
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