Automatic speaker recognition technology outperforms human listeners in the courtroom

A key issue in a number of court cases is whether a speaker on an audio recording is a particular known speaker, for example, whether a speaker on a recording of an intercepted telephone call is the defendant.

In most English-speaking countries, expert testimony is only admissible in court if it is likely to help the judge or jury reach a decision. If the identification of the speaker by the judge or jury was as accurate or more accurate than the forensic voice comparison of a forensic scientist, then the forensic voice comparison testimony would not be admissible. .

In a research article “Speaker identification in courtroom contexts — Part I”, recently published in the journal International Forensic Sciencesan international multidisciplinary team of researchers has reported the first set of results from an extensive study that compares the accuracy of speaker identification by individual listeners (such as judges or jury members) with the accuracy of a medical system -forensic voice comparison based on state-of-the-art automatic speaker recognition technology, using recordings that reflect the conditions of a real case.

The interviewed speaker’s recording was of a telephone call with office background noise, and the known speaker’s recording was of a police interview conducted in an echo room with voice system background noise. ventilation.

The forensic voice comparison system performed better than all 226 listeners that were tested.

The research team was made up of forensic data scientists, lawyers, experimental psychologists and phoneticians, based in the UK, Australia and Chile.

Corresponding author Dr Geoffrey Stewart Morrison, Director of the Forensic Data Science Laboratory at Aston University, said:

“A few years ago, while giving evidence in court, a lawyer asked me why the judge couldn’t just listen to the tapes and make a decision. Wouldn’t the judge do better than the forensic voice? comparison system that I used? It was the spark that drove us to conduct this research. I expected our forensic voice comparison system to work better than most auditors but was surprised when it actually worked better than all I’m glad we now have an answer too clear to the question posed by the lawyer.

Contributing author Dr Kristy A Martire, from the School of Psychology, University of New South Wales, said:

“Past experiences where we have successfully recognized familiar speakers, such as family members or friends, may lead us to believe that we are better at identifying unfamiliar voices than we actually are. This study shows that regardless of a listener’s ability to recognize familiar speakers, their ability to identify unfamiliar speakers is likely to be no better than a forensic voice comparison system.”

Contributing author Professor Gary Edmond, University of New South Wales School of Law, said:

“Unmistakable scientific findings are that the identification of unknown speakers by listeners is surprisingly difficult and far more error-prone than judges and others have appreciated. We should not encourage or allow non-experts, including judges and jurors, to engage in unduly error-prone speaker identification. . Instead, we should seek the services of real experts: specialized forensic scientists who use empirically validated and proven forensic voice comparison systems. »

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Material provided by Aston University. Note: Content may be edited for style and length.

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