Speaker profiling and forensic voice comparison

Abstract

Speaker profiles are requested by the police for the purpose of finding a suspect. Information useful for that purpose includes age, sex, region, social status, foreign-language background, as well as individual linguistic characteristics that are noticeable by laypersons. If recorded material from a suspect is available, it is possible for an expert to conduct a forensic voice comparison and use it as evidence in court. This chapter provides an overview of these two tasks within the field of Forensic Phonetics and Acoustics. Emphasis is given to auditory-phonetic and linguistic methods and to acoustic-phonetic methods. One of the points argued for is that this duality of method types, which is captured in the subtitle ‘The auditory-acoustic approach’, should apply not only to voice comparison but also to speaker profiling. This point is strengthened by including information on acoustic features when discussing the profiling-relevant classes of age, sex/gender and body height. An overview is given to some of the most important speaker-specific characteristics (fundamental and formant frequencies). This is followed by a presentation of the leading principles behind voice comparison and is concluded with references to international discussions about the status of the likelihood ratio approach in forensic voice comparison.