A Study On Reliability Of Suspects’ Statements In Police Interrogation

Suspects’ statements, as important evidence, once verified can be used as the basis for deciding cases. Therefore, the reliability of suspects’ statements is one of the decisive factors to determine whether the evidence should be admitted. The present thesis is a tentative study exploring a set of macro and micro verbal cues from the perspective of Discourse Information Theory(DIT) to distinguish the truthful statements and deceptive statements made by suspects in police interrogation.Descriptive and qualitative methods were employed in real data analysis to extract macro and micro verbal cues. In testifying the validity of the extracted cues in truthful and deceptive statements, quantitative method, for instance statistical methods such as t-test, Mann-Whitney, and ANOVA, are employed so as to obtain a valid verbal cue set. Macro-cues including information redundancy, information vacancy, uneven information development, subjective information knots, limited objective information knots, and two micro-cues, namely manner condition and limited elaboration condition, were found typical in deceptive statements.At last, an experiment in the form of mock theft case was conducted to testify the effectiveness of the verbal cue set and reveal the accuracy differences between polygraph and DIT method in discriminating truthful statements from deceptive ones. Thirty-one undergraduate and postgraduates, including 26 females and 5 males, participated in the experiments on volunteer basis. The results showed that the accuracy rate of the verbal cue set was significantly acceptable and higher than that of polygraph. Therefore, assessing the reliability of suspects’ statements from the perspective of DIT is feasible and effective.This research distinguishes itself from other deception detection study because of its new perspective, namely, the perspective of DIT. It enriches the study method of deception detection and the application of DIT, and hopefully can provide both theoretical and technical support for the linguistic evidence presented in court.