Whereas much of the limited research concerning the actual investigative interviewing of suspects has involved police interviews, almost no research has involved other agencies who increasingly are undertaking criminal investigations. The first study therefore examined 142 actual benefit fraud interviews, revealing that, whilst investigators generally displayed ethical interviewing standards, few interviews were skilled. Shortcomings were particularly found in terms of rapport development, summarising, and how investigators closed interviews. The second study (using the same sample as with the first study) examined whether there was any association between skilled interviewing and interview outcomes, finding that better interviewing conducted under the recommended interviewing framework, tended to be associated with better outcomes, whereas less skilled interviewing generally led to interviews resulting in untested denials or just partial admissions. Powerful effect sizes were regularly reported in the study. A third study focussed on the effects of rapport upon outcomes in investigative interviews. Rapport has been frequently cited in previous studies as a feature that improves the quality of interview performance of investigators and is likely to yield much further information from suspects. The third study examined whether the particular task of rapport, built and then maintained throughout the interview, had any association with interview outcomes. The study found that there was an association between better displays of rapport building and maintenance and those preferred interview outcomes (i.e., the obtaining of a comprehensive account from suspects or full and frank admission of wrongdoing). Effect sizes were frequently found to be strong. A further (fourth) study was then conducted to establish why the interviewing performance was so mediocre. 115 investigation personnel completed a questionnaire. This study found that, whilst there appeared to be an understanding of the essential components of interviewing, there was a considerable gap between perception and reality that was believed to be caused by inconsistent approaches to evaluation by senior officers and similar problems concerning the vital task of self-evaluation.
The fifth and final study, recognising that organisations (such as those studied in this thesis) necessarily tend to be more risk averse when making decisions to prosecute, examined the skill levels of prescribed tactics used, and attitude displayed, by interviewers and the extent of their presence in 85 interviews. The study found that there appeared to be an association both between the higher rated skill levels and the larger extent of the presence of these tactics and attitudes, when examined against increased shifts towards confessions. Effects sizes were found to be consistently strong in this final study. Nevertheless, as only one offence type was analysed, further research of interview performance in investigation organisations (both police and nonpolice) is vital.