This study evaluated the performance of three types of hand-held cellphone-detection devices in terms of their ability to locate contraband cellphones in a prison setting.
Overall, study results show that hand-held cellphone detectors could assist in countering inmate use of contraband cellphones; however, they should not be viewed as the sole solution to this problem. A multi-layered approach is recommended that includes sound policies, procedures, and proven technology solutions. The three types of hand-held cellphone-detection devices tested were RFD devices, which detect radio signals emanating from a cellphone; FMD devices, which detect the ferromagnetic components common in cellphones; and NLJD devices, which leverage the unique properties of semiconductors used in electronic products. RFD devices were useful in detecting cellphones at the time they were being used to make a call. Detection occurred at distances up to 125 feet from the cellphone in use. These devices were accurate 100 percent of the time. Both FMD and NLJD devices detected cellphones whether or not they were being used at the time of the testing, since they rely on the materials and components common in the cellphones themselves; however, the devices must be less than 8 inches from a cellphone for detection to occur. The NLJD device performed well at short ranges in the cell search scenario, with an accuracy of 94 percent, regardless of the status of the cellphone. Although the FMD device detected cellphones at short range, it produced a large number of false positives. 1 table and 2 notes