Police detectives, criminal investigations and collective moral responsibility

In this paper my concern is with the collective moral responsibility of criminal investigators for the outcomes of their investigations, bearing in mind that it is important to distinguish collective moral responsibility from, and relate it to, individual moral responsibility. In what sense, if any, are police detectives individually and collectively morally responsible for their success (or, for that matter, their failure) in gathering sufficient evidence to identify, arrest, and charge an offender who has committed a serious crime? Alternatively, in what sense are they morally responsible in cases where they identify, arrest, and charge an innocent person? And in what sense, if any, are police detectives individually and collectively morally responsible for the ultimate outcome of the trial, the finding by the courts of someone they have investigated and charged with a serious crime to be guilty or innocent?