Creating a Search Team

A metal detector serves as an invaluable tool in the search for and recovery of metallic evidence. Some law enforcement agencies rely on external groups to provide this service, but various concerns about crime scene integrity—for example, the chain of custody for evidence and required documentation of the search—can make this practice problematic. To ensure admissibility in court, individuals operating the detectors must be vetted, properly trained, and accountable to the agency. This reduces the chance of missing or mishandled important evidence.

In response to this issue, in 2014 the Orange County, California, Sheriff's Department (OCSD) established a metal detector search team. The agency made important considerations regarding equipment selection and the development of training for metal detector use. Other departments can use this information in their decision-making process when creating similar programs.

OCSD's metal detector search team comprises part of the search and rescue reserve unit (SRRU), one of many units in the reserve bureau. Except for the lieutenant and sergeant, the reserve bureau consists of a mix of reserve deputies—sworn law enforcement officers—and nonsworn professional service responders (PSRs). Both reserve deputies and PSRs are volunteers who passed background investigations before joining the department.

SRRU searches for lost people, crime scene evidence, and potential weapons in jail facilities. Because most weapons contain some amount of metal, a metal detector proves important for evidence searches. In 2014, SRRU began to standardize equipment and formalize training for metal detector operators.

Selecting Equipment

When the metal detector search team was created, detectors available to SRRU consisted of models that had appeared on the market around 2001. Since that time, detectors' electronics, coil design, target-discrimination logic, and operator interface have improved in various ways. These upgrades translate into better depth penetration to locate evidence buried deeper in the soil; greater ability to determine the type and size of a target; and improved displays and controls, making detectors easier to learn and use.

To select an ideal ground-search metal detector, departments must consider the design and features they will find most useful. There are two main types of metal detectors on the market today: induction balance (IB) and pulse induction (PI). Each has benefits and drawbacks. For example, the PI design is superior in saltwater environments, so a metal detector designed for underwater use typically uses PI. However, in general, the IB design is easier to use and provides the best overall performance for ground-search applications.

< read the complete article. >

This article was originally published in the April 2020 edition of the FBI Law Enforcement Bulletin. https://leb.fbi.gov/articles/featured-articles/metal-detectors-in-evidence-search-and-recovery