82 26. Combating impunity must start at home, that is within the agency (police or prison service, military authority, etc.) concerned. Too often the esprit de corps leads to a willingness to stick together and help each other when allegations of ill-treatment are made, to even cover up the illegal acts of colleagues. Positive action is required, through training and by example, to promote a culture where it is regarded as unprofessional – and unsafe from a career path standpoint – to work and associate with colleagues who have resort to ill-treatment, where it is considered as correct and professionally rewarding to belong to a team which abstains from such acts. An atmosphere must be created in which the right thing to do is to report illtreatment by colleagues; there must be a clear understanding that culpability for ill-treatment extends beyond the actual perpetrators to anyone who knows, or should know, that illtreatment is occurring and fails to act to prevent or report it. This implies the existence of a clear reporting line as well as the adoption of whistle-blower protective measures. 27. In many States visited by the CPT, torture and acts such as ill-treatment in the performance of a duty, coercion to obtain a statement, abuse of authority, etc. constitute specific criminal offences which are prosecuted ex officio. The CPT welcomes the existence of legal provisions of this kind. Nevertheless, the CPT has found that, in certain countries, prosecutorial authorities have considerable discretion with regard to the opening of a preliminary investigation when information related to possible ill-treatment of persons deprived of their liberty comes to light. In the Committee’s view, even in the absence of a formal complaint, such authorities should be under a legal obligation to undertake an investigation whenever they receive credible information, from any source, that ill-treatment of persons deprived of their liberty may have occurred. In this connection, the legal framework for accountability will be strengthened if public officials (police officers, prison directors, etc.) are formally required to notify the relevant authorities immediately whenever they become aware of any information indicative of ill-treatment.