  These powers and permissions exist ex ante—prior, that is, to the commission of crime. We can add those that exist ex post—once crime has been committed. Imagine now that \(D\) has \(\phi\)ed. As well as the power to arrest \(D\), the criminal law confers a set of investigative powers designed to help generate evidence of \(D\)’s criminality: these include powers to stop and search, to carry out surveillance, and to detain suspects for questioning. If sufficient evidence is produced, and it is in the public interest to do so, \(D\) may be charged with a crime. To exercise these powers is to impose new duties on \(D\)—\(D\) must submit to the search, remain in detention, and turn up in court when required. For \(D\) to do otherwise—absent justification or excuse—is itself criminal. So reasonable force can permissibly be used against \(D\) if she refuses to co-operate.