Police forces have a
discretionary power to remove details of a caution from the Police National Computer after 5 years but there's no obligation upon them to do so. Therefore, you have no rights, under the Data Protection Act, to complain if such information appears on a CRB check.
CRB checks (both Standard and Enhanced) are only available where the Exceptions Order, under the Rehabilitation of Offenders Act applies. (Generally, that means where the employee, or volunteer, will have close contact with children or vulnerable adults). A caution for theft (from many years ago) would be unlikely to 'set alarm bells ringing' with an employer, unless (for example) the employee had access to valuable items belonging to the elderly and confused residents of a care home.
http://www.crb.gov.uk/PDF/CRB_DIP017-Applicant s-Guide-to-the-CRB's-Disclosure-Service_Eng.pd f
Chris