Investigative interviewing is a core practice within a criminal investigation and is used by police officers to gather information and evidence from suspects, victims and witnesses of crime. The research presented in this thesis examines the process of conducting investigative interviews. It investigates the factors which shape interview practices focusing on whether there is a 'science' to interviewing - characterised by factors such as the integration of research, guidance and 'best practice' - or whether it is a 'craft' developed by police officers in the context of their day-to-day working routines and cultural understanding of police work. Utilising a criminological (and sociological) approach and qualitative research methodology (semi-structured interviews and observation), this research considers the function of investigative interviewing and how legislation and guidance (formal), research, training and supervision (organisational) - all designed to improve the interview process - and cultural practices (informal), are understood and applied in practice and used operationally in police officers' day-to-day work. The overall findings of the research suggest that although there is a 'science' to investigative interviewing as evidenced in the means of the production of guidance, models of interviewing, and legislation, it is still best understood as a 'craft' by officers. The accounts provided by officers in the course of the research suggested that investigative interviewing, or more specifically effective investigative interviewing, is a skill that is developed over time, and one which is shaped by the officers own experiences, learning from colleagues and through processes of socialisation (formal training and informal).