Following the success of a 12-month trial in 10 police forces, the Home Secretary agreed on 24 November 2008 to allow chief officers of all forces in England and Wales, from 1 December 2008, to extend the use of Taser to specially trained units in accordance with current Association of Chief Police Officers (ACPO) policy and guidance. This sets out that Taser can only be used by specially trained units where officers would be facing violence or threats of violence of such severity that they would need to use force to protect the public, themselves and/or the subject(s). The number of specially trained officers in each police force is a matter for individual chief officers based on their own operational requirements.