Introduction
Recent high-profile cases of police misconduct have revealed that officers were often aware of misconduct, but remained silent, compromising public trust in law enforcement. Here, we systematically review ‘police whistleblowing’ literature to identify barriers and facilitators to officers challenging misconduct.

Methodology
Employing PRISMA guidelines, we systematically reviewed 118 relevant papers, extracting data and coding key variables including who the ‘target’ of the research was; whether reporting practices were studied, and whether practical solutions were offered. A reflexive thematic analysis then assessed consensus among researchers within the literature.

Results
Five themes - 1) knowledge and rules, 2) consequences, 3) interpersonal relations, 4) responsibility, and 5) police culture and group relations – emerged as barriers and facilitators to whistleblowing. The review revealed relatively poorer representation of internal police reporting structures and limited practical solutions, with only 40 papers proposing strategies, predominantly centred on training and education.

Discussion
This review highlights methodological limitations in existing research, with an overreliance on survey methods and a dominant focus on the characteristics of individuals over the structural constraints of reporting. The positive impacts of whistleblowing on policing as an institution and the development of practical strategies to overcome officers' reluctance to report misconduct remain largely unexplored.