Assessing the missing data problem in criminal network analysis using forensic DNA data

• Forensic DNA data can be used to study missing data in network analysis. • Important advancement over previous studies on missing data in network analysis. • Police data on known offenders is integrated with DNA data on unknown offenders. • Unknown offenders have an impact on degree, but not on betweenness centrality. • Confirmation of importance of studying unknown offenders in social network analysis. Missing data is pertinent to criminal networks due to the hidden nature of crime. Generally, researchers evaluate the impact of incomplete network data by extracting or adding nodes and/or edges from a known network. Statistics on this reduced or completed network are then compared with statistics from the known network. In this study, we integrate police data on known offenders with DNA data on unknown offenders. Statistics from the integrated dataset (‘known network’) are compared with statistics from the police data (‘reduced network’). Networks with both known and unknown offenders are bigger but also have a different structure to networks with only known offenders.