Can I be arrested for questioning if I am not a suspect?

No. You can only be arrested if you are suspected of an offence. If the police believe that you might have information relating to a crime, they may ask you to attend a police interview; but you do not have to attend. However, if someone else is (or has been) charged, a Court document (called a ‘subpoena’) may be issued requiring you to: (a) attend Court to give evidence as a witness, or (b) produce requested documents if they are in your possession, custody or control