What does method validation look like for forensic voice comparison by a human expert?

Method validation has gained traction within forensic speech science. The community recognises the need to demonstrate that the analysis methods used are valid, but finding a way to do so has been more straightforward for some analysis methods than for others. This article addresses the issue of method validation for the Auditory Phonetic and Acoustic (AuPhA) approach to forensic voice comparison. Although it is possible to take inspiration from general regulatory guidance on method validation, it is clear that these cannot be transposed on to all forensic analysis methods with the same degree of success. Particularly with respect to an analysis method like AuPhA, and in a field of the size and characteristics of forensic speech science, a bespoke approach to method validation is required. In this article we address the discussions that have been taking place around method validation, and illustrate one possible solution to demonstrating the validity of voice comparison by a human expert using the AuPhA method. In doing so we consider the constraints placed on sole practitioners, which generally go unacknowledged.

Voicing concerns: The balance between data protection principles and research developments in forensic speech science.

The status of forensic speech recordings among existing data protection guidance is not clear. The inherent nature of voice and the way in which forensic speech casework is currently allocated mean that there are additional barriers to incorporating real casework data into research activities. The key objective of this work is to explore data protection solutions that could enable the forensic speech science community to responsibly use real casework data for research and development purposes. While reviewing relevant guidance and rulings, issues such as proportionality, opportunism and data minimisation are addressed, as well as where voice sits in relation to the definition of "biometric data". This paper ultimately places forensic speech recordings in the data protection context to illuminate the specific issues that arise for this data type.

Detecting suspicious behaviour using speech: acoustic correlates of deceptive speech -- an exploratory investigation.

The current work intended to enhance our knowledge of changes or lack of changes in the speech signal when people were being deceptive. In particular, the study attempted to investigate the appropriateness of using speech cues in detecting deception. Truthful, deceptive and control speech were elicited from ten speakers in an interview setting. The data were subjected to acoustic analysis and results are presented on a range of speech parameters including fundamental frequency (f0), overall amplitude and mean vowel formants F1, F2 and F3. A significant correlation could not be established between deceptiveness/truthfulness and any of the acoustic features examined. Directions for future work are highlighted.