Use of relevant data, quantitative measurements, and statistical models to calculate a likelihood ratio for a Chinese forensic voice comparison case involving two sisters

Currently, the standard approach to forensic voice comparison in China is the aural-spectrographic approach. Internationally, this approach has been the subject of much criticism. The present paper describes what we believe is the first forensic voice comparison analysis presented to a court in China in which a numeric likelihood ratio was calculated using relevant data, quantitative measurements, and statistical models, and in which the validity and reliability of the analytical procedures were empirically tested under conditions reflecting those of the case under investigation. The hypotheses addressed were whether the female speaker on a recording of a mobile telephone conversation was a particular individual, or whether it was that individual's younger sister. Known speaker recordings of both these individuals were recorded using the same mobile telephone as had been used to record the questioned-speaker recording, and customised software was written to perform the acoustic and statistical analyses.