Empirical test of the performance of an acoustic-phonetic approach to forensic voice comparison under conditions similar to those of a real case

- Aural-spectrographic forensic voice comparison testimony was presented in court.
- The analysis focused on F2 trajectories and mean f0 in /o/ tokens.
- No demonstration of validity and reliability was provided.
- We empirically tested an acoustic-phonetic analysis based on the same features.
- Under conditions similar to those of the case, the performance was very poor.

In a 2012 case in New South Wales, Australia, the identity of a speaker on several audio recordings was in question. Forensic voice comparison testimony was presented based on an auditory-acoustic-phonetic-spectrographic analysis. No empirical demonstration of the validity and reliability of the analytical methodology was presented. Unlike the admissibility standards in some other jurisdictions (e.g., US Federal Rule of Evidence 702 and the Daubert criteria, or England & Wales Criminal Practice Directions 19A), Australia's Unified Evidence Acts do not require demonstration of the validity and reliability of analytical methods and their implementation before testimony based upon them is presented in court. The present paper reports on empirical tests of the performance of an acoustic-phonetic-statistical forensic voice comparison system which exploited the same features as were the focus of the auditory-acoustic-phonetic-spectrographic analysis in the case, i.e., second-formant (F2) trajectories in /o/ tokens and mean fundamental frequency (f0). The tests were conducted under conditions similar to those in the case. The performance of the acoustic-phonetic-statistical system was very poor compared to that of an automatic system.