This chapter explores two key difficulties encountered in deciding to whom an agent should be accountable for the purpose of an ideal accountability benchmark. First, there are a multiplicity of factors that might influence a prosecutor’s capacity and interest to undertake that role (eg resources, skills and motives). Secondly, we will likely reach differing views on the best choice of prosecutor depending on which accountability rationale we are interested in promoting. So, for instance, if our goal is punishment of wrongdoing we might think it appropriate that this is managed by a state prosecutor to reinforce the seriousness of a transgression. On the other hand, if our goal is to control public power we might think it appropriate to have a very open regime in order to maximise the likelihood that a prosecutor will volunteer for the task. It would be necessary to confront and resolve these difficult questions in order to define a benchmark of accountability.