Prosodic profiles: Suspects' speech during police interviews

This dissertation presents a descriptive study of the prosodic characteristics of suspects' speech during investigative interviews with police. During police interviews, investigators direct conversation by asking suspects questions and making assertions which place the suspect in the position of responding. Based on whether the suspect is a first-time or repeat offender, and the type of information suspects produce, responses are categorized and examined for their properties of pause, tempo, and pitch. Response categories explored in this study are affirmative, in which suspects confirm information in the investigators' questions or assertions; negative, in which asserted information is rejected; relevant and irrelevant, in which suspects offer information pertaining or not pertaining to the investigators' questions; and confessions. Certain pausal features—response latency, pause-to-speech ratio—are found to differ across response types in both groups. In general, for example, first time suspects pause more than repeat offenders, both before and during turns, particularly when offering relevant information. Among the temporal features, first time suspects' speech and articulation rates are lower when producing relevant information than repeat offenders' rates. Furthermore, first-timers' irrelevant temporal rates are higher than relevant temporal rates. Pitch characteristics show less distinction across response types than pause and tempo, although first-time suspects' pitch values cluster somewhat more neatly within response types than repeat offenders', whose pitch values vary more widely.