What does the law of NSW say about lie detector tests in court?
Without definitive evidence, the credibility and reliability of witnesses can play a significant role in how a case is decided in court. However, determining what witnesses to believe can be a difficult task. Polygraph tests, also known as ‘lie detector tests’, have been a perennial fixture in crime novels, films and TV shows for decades. But do they actually work? Can lie detector tests be used in court in NSW? Let’s take a look.
Polygraph machines work by measuring a person’s physiological reactions when they answer questions. Reactions are measured in one of two ways:
Though polygraph machines are a standard feature in popular culture, they aren’t as valid or accurate as we are led to believe. Different people often react in a variety of ways to intense questioning, especially if they know they are having their answers recorded and measured. Importantly, lie detectors can only measure physiological stress responses, not the source of this stress, which could simply result from being subjected to a polygraph in the first place. The test therefore cannot tell definitively that a person has ‘lied’, and may report an erroneous result just because the person is nervous. In addition, some people are able to ‘beat’ a lie detector test by purposefully altering their physiological state.
In the 1981 case of R v Murray, the District Court of New South Wales ruled the results of a lie detector test inadmissible. The accused, Raymond George Murray, denied an allegation that he fired shots at police officers. During the course of the trial, the accused attempted to adduce evidence of the results of a polygraph examination that he undertook in an aim to substantiate his denial of the charges. Murray sought to call a polygraph examiner who would give evidence that in his opinion, the accused was speaking the truth and that his denials were true.
In response, District Court Judge Sinclair decided that the evidence was not admissible for the following reasons:
District Court Judge Sinclair ultimately concluded that admitting such evidence would be contrary to the basic principles of evidence law in New South Wales, and though such a technique “no doubt holds a genuine fascination for some people” it “has no place in a criminal trial in New South Wales”.
Following the case, the Lie Detectors Act 1983 (NSW) was implemented in NSW. The Act regulates instruments that measure or monitor the physiological reactions of the body of another person, or elements of stress, tonal variation or vibration in the voice of another person. s 6(1) of the Act provides that any output from such a test, or analysis of the output of the test, is inadmissible as evidence in court, even if the parties consent.
Interestingly, the Lie Detectors Act 1983 (NSW) makes it an offence to use a polygraph test in any of the following situations:
Using a lie detector in any of these situations can result in a fine of up to $1,100, or $5,500 if the offender is a corporation. The fine can double in the case of a second or subsequent offence.
Though evidence from a polygraph is inadmissible in court, the Act does not prohibit police from using such testing during their investigations.
In an interesting case heard in 1986, a man argued that the magistrate wrongly admitted the results of a breath analysis in a case of high range drink driving because the instrument was prohibited by the Lie Detectors Act 1983 (NSW). The man submitted that there is a “physiological reaction” when a person is asked to breathe into the breathalysing instrument, and therefore the Lie Detectors Act applies. Accordingly, what the police officer did in taking the information from the machine and putting it on to a certificate was forbidden and could not be used in evidence in the proceedings.
However, the NSW Court of Criminal Appeal was not convinced, and found that the man had overlooked that the Lie Detectors Act is “concerned with one subject matter and one subject matter only, that is lie detectors.” To seek to apply the Act as the man had attempted, was, according to the Court, “manifestly absurd”, because a breath analysis tool has nothing to do with the detection of lies.