Until now, the prison service, police forces and immigration units have not been subject to the new Corporate Manslaughter and Homicide Act, and there have been no successful prosecutions of police or prison officers, individually or at a senior management level, for institutional failures that have contributed to a death in custody.

But from 1 September a clause in the Corporate Homicide Act 2007 will come into place extending the law to cover all deaths in police custody suites, prison cells, mental health detention facilities, young offenders institutions and immigration suites. It will also cover Ministry of Defence institutions.

Prosecutions will take place if it can be proved that the way the facilities are managed or organised caused a death and amounted to a breach of the duty of care. The penalty for organisations convicted is a fine with no maximum limit. Crown Prosecution Service guidance says that the fines are likely to be in the many millions of pounds.

Deaths of people being transported to and from immigration detention centres – such as that of Jimmy Mubenga – will also be covered by the Corporate Homicide Act. But in the case of Mubenga, who died while being restrained on a British Airways plane to Angola last year, the private firm hired to transport him cannot be prosecuted under the Act because the law is not retrospective.