The chapters in this part of the book look at such issues as covert surveillance and informant handling, the treatment of victims and witnesses, investigative interviewing, offender and geo-demographic profiling. David Carson’s opening chapter examines different approaches to the task of investigation. He questions the extent to which it is appropriate to think of investigation as a scientific process and examines the nature and reliability of expert evidence. Carson analyses decision-making processes and, following a number of other contributors, notes that there is now a balance to be struck between analyses of evidence and the assessment of risk. The rise of risk-based assessment, at least as a basis for the management of investigation, has been paralleled by the emergence of an audit-based approach to criminal investigation. This focuses on the quality, and by implication, cost-effectiveness, of the ‘factfinding’ processes. In the event, Carson favours such a model, largely for its potential to enhance not only the investigative process but also the status and reputation of such work.