Speaker identification in courtroom contexts - Part II: Investigation of bias in individual listeners' responses.

In "Speaker identification in courtroom contexts - Part I" individual listeners made speaker-identification judgements on pairs of recordings which reflected the conditions of the questioned-speaker and known-speaker recordings in a real case. The recording conditions were poor, and there was a mismatch between the questioned-speaker condition and the known-speaker condition. No contextual information that could potentially bias listeners' responses was included in the experiment condition - it was decontextualized with respect to case circumstances and with respect to other evidence that could be presented in the context of a case. Listeners' responses exhibited a bias in favour of the different-speaker hypothesis. It was hypothesized that the bias was due to the poor and mismatched recording conditions. The present research compares speaker-identification performance between: (1) listeners under the original Part I experiment condition, (2) listeners who were informed ahead of time that the recording conditions would make the recordings sound more different from one another than had they both been high-quality recordings, and (3) listeners who were presented with high-quality versions of the recordings. Under all experiment conditions, there was a substantial bias in favour of the different-speaker hypothesis. The bias in favour of the different-speaker hypothesis therefore appears not to be due to the poor and mismatched recording conditions.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dr Morrison is Director and Forensic Consultant for Forensic Evaluation Ltd. Dr Weber has worked as a contractor for Forensic Evaluation Ltd. Forensic Evaluation Ltd charges clients fees to perform forensic-voice-comparison evaluations, and to submit reports and testify in court regarding forensic voice comparison, and regarding speaker recognition and speaker identification by laypersons.
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