The short answer
If you are asking whether polygraph evidence can be used in an Australian court, the position in the reported cases is that it has not been accepted. The leading decision is a Western Australian appeal judgment from 2003.
This guide is based on that one judgment. It does not review every Australian jurisdiction, so treat it as a starting point and confirm the current position with a lawyer in your state or territory. This is not legal advice.
Mallard v The Queen [2003] WASCA 296
The Court of Criminal Appeal of Western Australia (Parker, Wheeler and Roberts-Smith JJ) delivered this judgment on 3 December 2003. The petitioner argued, among other things, that his lawyer should have led polygraph evidence at his trial. To decide that, the court had to decide whether the evidence would have been admissible.
| Issue | What the court found |
|---|---|
| The position | Polygraph evidence was inadmissible at the time of the trial, and the court said that remains the position in Australia. |
| The nature of the evidence | A polygraph examiner gives an opinion on whether a person is truthful, which, in the court's words, goes directly to whether the petitioner is truthful. |
| Scientific acceptance | The court was not satisfied that polygraphic examination had gained recognised scientific acceptance, and noted that supporting publications came mainly from polygraph examiners with a vested interest. |
| Reliability | The court said it had not been shown that the polygraph technique is a reliable method for determining truth. |
| The technique itself | The court preferred the experts who said the question-based technique lacked an overarching theory and was subjective, and it found the scoring software unreliable. |
| The conclusion | The polygraph evidence was not admissible and would not have been admissible at the trial, so the lawyer's decision not to lead it was not an error and that ground of appeal failed. |
The court noted that polygraph evidence had not been admitted in any reported Australian case, and referred to earlier authority excluding it, including a 1981 decision.
What the court did not say
- It did not say new science is never admissible. The court said expert opinion should not be rejected merely because a technique is new, and that admissibility may change as science develops.
- It did not decide every jurisdiction. This was a Western Australian appeal decision reasoned mainly on common-law principles and comparative authority. Other states, territories and the federal courts may apply different rules or statutes.
- It does not cover non-court uses. Employers, insurers and others may use polygraphs for their own purposes, subject to their own rules.
Why courts are cautious
- The reliability question. Accuracy is disputed. The US National Research Council found polygraph accuracy "well above chance, though well below perfection," and that anxiety about being tested can distort results. See how accurate a polygraph really is.
- It speaks to credibility. A polygraph is offered as an opinion on whether someone is telling the truth, which is the question a court has to decide itself.
- Subjectivity. Scoring involves judgment, which makes results hard to test.
What this means if you are involved in a case
- Do not count on a polygraph to prove your case.On the Mallard reasoning, a favorable result is unlikely to be admitted or to carry weight.
- Speak to a lawyer in your state before taking or offering a test.Ask whether it could help, hurt or simply be ignored.
- Watch what you say in interviews.Statements in a pre-test or post-test interview can have consequences whatever the test shows. Be accurate and consistent.
- Keep every document.The report, the questions and any recording.
- Do not assume the law is unchanged.A 2003 decision is a guide. Ask what the current position is.
Related reading
Compare with US courts and Philippine courts. For the science behind the doubts, read why polygraphs fail innocent people.
This guide is general information based on one court of appeal judgment, not legal advice. Australian law differs by state and territory and may have developed since 2003. The judgment copy linked in the sources is hosted by a third party; check the official law reports or an Australian legal database for the authoritative text.
Frequently asked questions
Are polygraph results admissible in Australian courts?
What did the court decide in Mallard?
Why was the polygraph evidence excluded?
Is Mallard the last word on polygraphs in Australia?
Can a private polygraph help my case?
Sources
A polygraph in a legal matter in Australia?
A lawyer in your state advises on evidence and strategy. In a private 1-on-1 session we can explain how the test works and what a result does and does not show, so you can ask your lawyer informed questions.