A registry of child maltreatment perpetrators would be useful primarily in identifying past maltreatment by parents. It would not generally be useful in identifying those who abuse or neglect unrelated children. While nearly all state registries include parents and legal guardians, fewer (60 to 70 percent) include foster parents, relatives, staff of residential facilities and group homes, and child care providers. Unmarried partners of parents are included in 59 percent of states' registries. Few states include in their registries teachers or educational staff, other professionals, or friends/neighbors who have been found to have abused children with whom they have come into contact. This is because investigations of such other persons are generally conducted through the criminal justice system rather than by child protective services agencies. Existing criminal background check processes would detect such other persons who had been convicted of crimes against children.