'Off track' police investigations, case construction and flawed forensic practices: an analysis of three fatal stabbings in Sweden, California and England

Occasionally, internal and external pressures can result in police investigations going ‘off track’. Cases that are initially difficult to solve or where the police have been subject to negative media attention, may be particularly susceptible to this. ‘Off track’ police investigations increase the risk of tunnel vision and case construction, where the focus is to build a case against a police suspect which is likely to ignore or reject evidence that points to that suspect’s innocence. This article explores the problems associated with this by analyzing three fatal stabbings, from three different jurisdictions. The murder of a prominent politician in Sweden provides an example of good practice, in contrast to the murders of two young female victims, in California and England respectively, which provide examples of police investigations going ‘off track’. The article concludes that courts in the United States of America (US) and in England and Wales (E&W) need to be more alert to substandard practices within investigations. In particular, courts need to acknowledge problems that can be expected to arise through case construction. The authors suggest a need for extreme caution when prosecuting cases based on circumstantial evidence alone, particularly where the crime itself is of such a nature that it could be expected to have left scientific evidence, and where the lack of such evidence may in fact undermine the circumstantial case against the suspect.