Information retrieval in systematic reviews: a case study of the crime prevention literature

A defining feature of a systematic review is the data collection; the assembling of a meticulous, unbiased, and reproducible set of primary studies. This requires specialist skills to execute. The aim of this paper is to marshal tacit knowledge, gained through a systematic search of the crime prevention literature, to develop a 'how-to guide' for future evidence synthesists in allied fields. Empirical results from a recent systematic search for evidence in crime prevention are supplied to illustrate key principles of information retrieval. Difficulties in operationalizing a systematic search are expounded and possible solutions discussed. Empirical results from optimizing the balance between sensitivity and precision with the criminological literature are presented. An estimation of database overlap for crime prevention studies is provided to guide other evidence synthesists in streamlining the search process. A high-quality search will involve a substantial time investment in honing the research question, specifying the precise scope of the work, and trialing and testing of search tactics. Electronic databases are a lucrative source of eligible studies, but they have important limitations. The diversity of expression across the criminological literature needs to be captured by the use of many search terms-both natural language and controlled vocabulary-in database searches. Complementary search tactics should be employed to locate eligible studies without common vocabulary. Grey literature should be ardently pursued, for it has a central role in the crime prevention evidence base.