The choked, panicked words ‘I shot the prick!’ recorded in an emergency call played at a murder trial would have been significant evidence … unless what the man actually said was ‘I can’t breathe!’ Deciphering indistinct recordings requires expertise in phonetics, arguably the least known of the forensic sciences – but Australian law gives the task to detectives, calling them ‘ad hoc experts’.

Dr Helen Fraser, who is not involved in this dispute, has lectured on phonetics in universities for almost two decades and is now an independent researcher, helping courts to ‘hear the truth’ in covert recordings. She believes that proper expertise hardly ever means the police, whose transcriptions are far too prone to cognitive bias, not to mention lacking in scientific probity.

In her experience, ‘creating a reliable transcript of indistinct audio is a specialised task, requiring real, not “ad hoc”, expertise’.

Yet now police have ad-hoc experted that pro-Palestinian protesters on October 9, 2023 at the Opera House were not chanting ‘Gas the Jews!’ but were looking for directions to the nearest Jews, chanting (ungrammatically): ‘Where’s the Jews!’ It is obvious that police did not provide directions, as the chants continued.

Australian police is investigating after videos emerged of yesterday's gathering in front of the Sydney Opera House where crowds of Hamas supporters were chanting "gas the Jews".

?? pic.twitter.com/Gap4FgWQ5u

— Visegrád 24 (@visegrad24) October 10, 2023

It is my opinion that this interpretation by police is an insult to the public’s intelligence.

NSW Police have confirmed they found no evidence of protesters chanting "gas the Jews" during a pro-Palestine rally at the Sydney Opera House in October | @nswpolice

Instead, police have confirmed protesters were chanting "Where's the Jews". pic.twitter.com/gIhM8bywYq

— 10 News First Sydney (@10NewsFirstSyd) February 1, 2024

As one expert in the field has pointed out previously, ‘Listening many times is necessary, but far from sufficient. What gives detectives the appearance of special ability is not the fact they have listened many times, but the fact they have background information and expectations about the recording. While such background may sometimes give police reliable insight about parts of an indistinct recording, it is a double-edged sword, which may mislead detectives as easily as assist them.’

Listen for yourself, and see if you agree with the police expert.

Andrew L. Urban publishes wrongfulconvictionsreport.org and is the author of books on miscarriages of justice.