Read the passage and answer the question. "Riverbend County Detention Center Policy 4.12 — Contraband Screening. Every person taken into custody is screened for contraband after the booking process is complete and before that person is escorted into the housing area. The screening exists to protect three groups: staff members, members of the public who visit the facility, and the people already housed inside. Only persons newly arriving from the field are treated as possible carriers of contraband; visitors are screened separately under Policy 4.13, and housed inmates returning from the exercise yard are not re-screened under this policy." According to the memo, the screening required by Policy 4.12 is intended to protect which group or groups?