A Study On Reliability Of Criminal Witness Testimony In Police Questioning Process

Witness testimony is the statement witness makes when questioned about thecase information he or she knows by the investigator, prosecutor or the judge. As onepiece of the most common evidence, witness testimony can reveal true facts and thusplays an important role in breaking cases. However, whether it can be the key part insolving a case or be adopted as evidence in court is to a large extent determined by itstruthfulness or reliability. And it has a strong influence on the clearing up criminalcases. In western countries the most frequently used linguistic technique to evaluatethe truthfulness of witness testimony is the Criteria-Based-Content-Analysis (CBCA)and has been used in the investigation process in some countries.Based real data analysis, adopting the theoretical method and experimentalanalysis, the present study is going to explore the verbal cues of truthful witnesstestimony in criminal cases during the police questioning process. Depending uponprevious studies and data analysis, the study extracts seven verbal cues which can beclassified into two parts, namely linguistic content (being logical, context, detailedinformation, perceptual information and subjective judgment) and linguistic form(harmonious references· use and information structure). The author explained theexistence of those cues by mental process theory in psychology and legal informationstructure in forensic linguistics. The experiment is designed to reveal the effectivenessof CBCA in China and that of those extracted verbal cues in distinguishing betweentruthful witness testimony and false ones.The experiment in this research was conducted in the form of mock criminal case.Applying the polygraph test method and discourse analysis method, the author tried toreveal the accuracy differences between polygraph and linguistic techniques indistinguishing between truthful witness testimonies and fabricated ones. And theauthor was to explore the linguistic strategies that truth tellers and liars adopted whenlying or telling the truth through the questionnaire analysis. Participants that took part in this empirical research included12females and4males and were divided into twogroups, with8members in each group. They were all postgraduates students inDGUFS and majored in English. The result showed that the accuracy rate of CBCA inestimating truth was62.5%but this linguistic technique would also cause the falsepositive result, i.e. liars were estimated as truth tellers. Half of the participants inGroup2(50%) were estimated as truth tellers in this empirical research, who wereactually liars. The accuracy rate of polygraph test in each group was both75%. In theestimation through the new indicators analysis, comparing the total score of eachgroup member with the number9(the mean score), the author found that the accuracyrate by this linguistic technique was87.5%. Thus it can be seen that to estimate thereliability of witness testimony by linguistic techniques is feasible and effective.While the questionnaire showed that participants in both groups believed that theywould offer detailed information as much as possible to persuade others to believe intheir words. Therefore, in distinguishing between truthful statements and fabricatedones, the estimator needs to pay due attention to this point.Since the present study comes into the domain of forensic psycholinguistics, theauthor hopes that more scholars can pay their attention to this new field and putforward the application of forensic linguistics in judicial practices in China.