Accounts of police complainants and their experiences of oversight largely reflect North American data. This article examines how complainants fare in Ireland, where police crisis and reform have repeatedly occurred since 2005. Quantitative analysis of the independent police oversight agency’s complaint processing highlights patterns in allegations submitted, complaint-handling mechanism applied, and outcomes realised. In doing so, this article draws attention to the experiences of Irish Travellers, the homeless and prisoners. Findings show that socially marginal complainants submitted more serious allegations, secured higher investigation designations but were less likely to have complaints substantiated. Overall, substantiation was below international levels and police investigations were more likely to substantiate complaints than was the oversight agency. Consequently, the article then considers the frequent theoretical characterisation of police oversight in term of ‘justice’ or ‘agency’, arguing for inclusion of ‘agency self-interest’ by the oversight body in future research.