Searching for prohibited items in mental-health hospitals: A randomised controlled trial of two metal-detecting technologies

Abstract

Weapons and other items with potential to cause harm are usually prohibited in mental-health hospitals and other psychiatric facilities. Detecting such prohibited items (PIs) can be problematic, particularly if concealed, and metal detectors are commonly used to search for such items. Our study compared two types of metal detection: continuous wave detection (CWD) by hand-held metal detector (HHMD) and magnetic anomaly detection (MAD) by a static pole device. In the study, real and dummy PIs were hidden on test subjects and in a simulated body cavity. The results showed MAD to be significantly superior to CWD in detecting small concealed PIs containing ferrous metal. The MAD pole found 100% of the real PIs on the test subjects and in the simulated body cavity. The CWD HHMD found only 5.2% of the real PIs, and these were limited to those on the test subjects, as it detected none in the simulated body cavity. In addition, the time taken to search by MAD pole was shorter than time taken to search by CWD HHMD.