Interviewees need to be supported to remember and articulate their experiences accurately and completely in investigative interviews. A rich account, elicited with a high-quality interview, can assist investigation, and increase the likelihood that the case will progress onward in the criminal justice system. The process of reporting personal and sensitive information, like sexual abuse, can be both cognitively and emotionally demanding for interviewees. Interviewer socio-emotional support in the form of supportive behaviours and strategies can help create an environment conducive to sharing. However, in comparison to other types of sensitive conversations (i.e., therapeutic interactions), forensic interviewers must consider additional parameters (e.g., neutrality of interviewer) when providing socio-emotional support in investigative interviews. Before supportive behaviours and strategies can be trained and used in the field, extensive research is needed to vouch for their effectiveness. While considerable research has explored how interviewers can best support child and adult interviewees in investigative interviews, the evidence is still not entirely conclusive. Three notable gaps remain in the research: a) ambiguity about what, how, when, and why supportive behaviours are used, b) incomplete understanding of participant perceptions regarding support behaviours or strategies used in their interviews, and c) a lack of guidelines for how interviewers should conduct preparatory phases with adults. This thesis comprises three studies which aimed to evaluate the utility, effectiveness, and perceptions of a variety of supportive behaviours and strategies for non-child interviewees. [...]