This paper considers the role of a Behavioural Investigative Adviser (BIA) in assisting with the decision‐making of a Senior Investigating Officer (SIO) in difficult‐to‐detect murder investigations. It outlines the need for transparent evidence‐based decision‐making from both the SIO and the BIA. The paper then details a piece of relevant, applied research that can assist in this end. The research utilised a pragmatic psychology approach to analyse 312 detected murder cases from the Serious Crime Analysis Section database. Some significant patterns relating what is known about the offence at different stages of an investigation and inferences regarding the offender were found, indicating that certain offence information can lead to some reliable predictions and these can be refined as more information becomes available. However, the findings also indicate that base rate frequencies and a ‘best‐guess’ methodology may be as, if not more, useful than more complex statistical techniques when providing advice to investigations. Copyright © 2013 John Wiley & Sons, Ltd.