The growing uptake of technology in policing provides the opportunity to revisit police-citizen interactions. This paper explores police-citizen interactions from a socio-technical systems perspective, drawing on community policing in the HCI literature, as well as the experience of both citizens and the police. For the latter, we report on a qualitative study with 29 participants including citizens, parish councilors, and police officers in England. Our findings use a socio-technical systems lens to highlight both social and technological challenges in police-citizen interactions, leading to several implications for practice and HCI design. These challenges include those arising from divergent viewpoints, power, and information imbalances between stakeholders, and technical systems that duplicate functionality or limit police-citizen interactions. Thus, our work contributes to extending HCI insights into the socio-technical infrastructure of policing contexts, and a better foundation for future research in the design and use of technologies to enhance community policing.