The idea of detecting deception from speech is very attractive from a law enforcement perspective, yet research considering the possibility has yielded conflicting results, due to the practical difficulties in investigating the topic. Scientific research is yet to provide forensic linguistics with a reliable means of discerning lies from truths. The present study explores the relationship between truthfulness and pausing behaviour. Various aspects of the acoustics of pausing behaviour were investigated for Standard Southern British English in 30 mock police interviews from the DyViS database. A novel distinction was made between prescribed and unprescribed lies, to delineate a potential source of differences in the unscripted content of speakers’ untruthful responses. Among pause duration measures, statistically significant differences were found across all three response types (truth, prescribed lie, unprescribed lie) for response latency, between truths and lies for initial filled pauses, and between unprescribed lies and the other response types for silent pauses. For pause frequency measures, only internal filled pauses showed a statistically significant difference: truths differed from both types of lies, but prescribed lies did not differ from unprescribed lies. Theories of cognitive effort and attempted control are drawn on in accounting for these findings.

The DyViS database provides recordings of 100 male speakers of Southern Standard British English, aged 18–25, from the University of Cambridge, undertaking four spoken tasks. The current investigation analyses recordings from Task 1, a mock police interview in which the participant assumes the role of suspect in a drug-trafficking crime. The participant views PowerPoint slides containing information about the crime scenario such as names of people and information about them, street names and venues, timing of events, etc. Most of the information is coloured black on the slides: these are details which the suspect is free to talk about. Some information is given in red: these details the suspect is required to lie about or conceal. Since interviewer style may affect speaker behaviour unpredictably (Dunbar, Jensen, Burgoon, Kelley, Harrison, Adame and Bernard 2015; Burgoon and Buller 2015), in the present study, the interviews undertaken by only one of the two DyViS interviewers (Gea de Jong) were used. Thirty interviews (DyViS Speakers 46–54, 56, 58–60, 62–65, 68, 69, 71, 73, 75–79, 84, 85, 87, 93) were analysed.

The data were collected manually using recordings imported into Praat (Boersma and Weenink 2020). An Excel spreadsheet was used to collate the data and organise results according to response category (T, PL, UL).

The present analysis, adopts a categorisation between truthful (T) and false answers, and whether the false responses were prescribed (PL) or not (UL). The T responses in the present study are all prescribed truths as the elicitation technique did not prompt a sufficient number of unprescribed truths for analysis. The distinction between prescribed and unprescribed lies may mirror the real-life circumstance of whether the suspect has prepared an alibi before police interrogation, with prescribed lies corresponding to responses based on their preprepared alibi, and unprescribed lies reflecting responses to unforeseen questions which have not been preconceived as part of their alibi. This provides a potential transferability between this novel experimental variable and real-life situations.