Employers need to identify candidates who may be unsuitable for certain jobs, especially work that involves vulnerable groups including children.
The Disclosure and Barring Service (DBS)  provides criminal records checking and barring functions  to help employers make safe recruitment decisions. This is supported by National Safeguarding Children and Safer Recruitment in Education Guidance 
Referrals and Barring
Expert caseworkers process referrals from employers and organisations about individuals who have harmed or pose a risk of harm to vulnerable groups, including children.
It is then decided who should be placed on the children’s barred list and/or adults’ barred list and prevented by law from working with these groups.
Criminal Records Checking
The criminal record checking service allows employers to access the criminal record history of people working, or seeking to work in certain positions, especially those that involve working with vulnerable groups.