Witness means
“Witness” means a person (other than a defendant)—
(4)(a)who has witnessed conduct in relation to which he may be or has been called to give evidence in relevant proceedings;
(b)who is able to provide or has provided anything which might be used or has been used as evidence in relevant proceedings; or
(c)who is able to provide or has provided anything mentioned in subsection (5) (whether or not admissible in evidence in relevant proceedings).
(5)The things referred to in subsection (4)(c) are—
(a)anything which might tend to confirm, has tended to confirm or might have tended to confirm evidence which may be, has been or could have been admitted in relevant proceedings;
(b)anything which might be, has been or might have been referred to in evidence given in relevant proceedings by another person;
(c)anything which might be, has been or might have been used as the basis for any cross examination in the course of relevant proceedings.
(6)For the purposes of subsection (4)—
(a)a person is a defendant in relation to any criminal proceedings if he might be, has been or might have been charged with or convicted of an offence in the proceedings;
(b)a person is a defendant in relation to any other relevant proceedings if he might be, has been or might have been the subject of an order made in those proceedings.
(7)In subsections (4) to (6) “relevant proceedings” means—
(a)criminal proceedings;
(b)proceedings of any other kind in respect of anti-social behaviour.
Domestic Violence, Crime and Victims Act 2004 [United Kingdom]