The police do not owe a duty of care to protect victims from the criminal acts of a third party when investigating or suppressing crime save in exceptional circumstances. This is justified as an application of the omissions principle and on several other grounds. The article argues that most of these justifications are unconvincing and it sets outs a positive rationale for the imposition on the police of a duty of care in respect of sufficiently proximate victims of a negligent omission. The scope of this duty can be coherently delimited by re-adjusting the existing framework of negligence liability of public authorities.