The Rehabilitation of Offenders Act 1974 (1978 Order in NI) provides that, after a period of time, the criminal convictions of a person are in many cases “spent” i.e. they are no longer deemed relevant and need not be declared to prospective employers, nor should they be disclosed under criminal records vetting procedures.

There are, or have been, some exceptions to spent convictions in caring sectors, where convictions never become spent for jobs working with, for example children and vulnerable adults. Employers may apply for Enhanced Criminal Record Certificates, where all convictions, no matter how trivial or old, are made known to employers in these caring professions. 

One of the respondents here ('T') had a caution for stealing a bicycle when he was 11 - it was declared to prospective employers when he wanted to work with children. The other ('JB') stole some false fingernails. She was refused work after the warning was declared to prospective employers.

By majority, the Supreme Court has found the disclosure of all convictions without further information exposed the prospective claimants to arbitrariness, was disproportionate and was not necessary to protect children or vulnerable adults (or, indeed, society as a whole) and therefore violated their right to respect for their private life under article 8 of the European Convention for the Protection of Human Rights and Fundamental Freedoms:
http://bit.ly/1njClUS 

As ever, the summary of the decision of the Supreme Court is on YouTube:
http://www.youtube.com/watch?v=zBFfkMof2j0&list=UUdkf93h71xVAl28v467Hk7w