This paper examines citations in legal documents in the context of bibliometric-enhanced legal information retrieval. It is suggested that users of legal information retrieval systems wish to see both scholarly and non-scholarly information, and legal information retrieval systems are developed to be used by both scholarly and non-scholarly users. Since the use of citations in building arguments plays an important role in the legal domain, bibliometric information (such as citations) is an instrument to enhance legal information retrieval systems. This paper examines, through literature and data analysis, whether a bibliometric-enhanced ranking for legal information retrieval should consider both scholarly and non-scholarly publications, and whether this ranking could serve both user groups, or whether a distinction needs to be made.Our literature analysis suggests that for legal documents, there is no strict separation between scholarly and non-scholarly documents. There is no clear mark by which the two groups can be separated, and in as far as a distinction can be made, literature shows that both scholars and practitioners (non-scholars) use both types.We perform a data analysis to analyze this finding for legal information retrieval in practice, using citation and usage data from a legal search engine in the Netherlands. We first create a method to classify legal documents as either scholarly or non-scholarly based on criteria found in the literature. We then semi-automatically analyze a set of seed documents and register by what (type of) documents they are cited. This resulted in a set of 52 cited (seed) documents and 3086 citing documents. Based on the affiliation of users of the search engine, we analyzed the relation between user group and document type.Our data analysis confirms the literature analysis and shows much cross-citations between scholarly and non-scholarly documents. In addition, we find that scholarly users often open non-scholarly documents and vice versa. Our results suggest that for use in legal information retrieval systems citations in legal documents measure part of a broad scope of impact, or relevance, on the entire legal field. This means that for bibliometric-enhanced ranking in legal information retrieval, both scholarly and non-scholarly documents should be considered. The disregard by both scholarly and non-scholarly users of the distinction between scholarly and non-scholarly publications also suggests that the affiliation of the user is not likely a suitable factor to differentiate rankings on. The data in combination with literature suggests that a differentiation on user intent might be more suitable.Algorithms and the Foundations of Software technolog
