More volunteers are needed to check on custody cells in Humberside police stations.
Pairs of "custody visitors" make random checks on the way officers respect the rights of detainees.
Humberside Police Authority currently has 30 visitors but says it needs to recruit more in order to create a better informed view on how detainees are treated.
Candidates will be interviewed and those selected will be trained.
Each custody visitor is expected to carry out at least six inspections a year.
Colin Inglis, who chairs the police authority, said: "We want to ensure that we have a cross-section of age, gender and ethnicity to give us total impartiality.
"It is both a rewarding and demanding opportunity which many people will find interesting and fulfilling."