The potential volunteer must give written permission for a criminal record check. The police may charge a fee for this service so there should be a clear policy about who should pay for this. While criminal record checks and screening are not foolproof, they are a good deterrent to those who fear a background check and may detect people who could be a threat to children. Your organization must be aware of potential legal liability if personal information about someone is made public. Even if something that is said is true, telling it to others, like another staff member, may still constitute an invasion of privacy which could result in a lawsuit.
Spoken defamation is called slander and written defamation is called libel.
Both refer to information that is made public which is judged to injure a person's reputation. Deciding when to say 'No' It is important to remember that the position is the issue, not the personal characteristics of the applicant. Any decisions that are made about exclusion should be based on what the position requires. Anytime a candidate is denied a position it should be for a legitimate reason which can be supported. For example, your organization has carefully determined what is appropriate or necessary for a certain position and makes decisions on that basis.