Most conducted-energy devices (CEDs) carried by law enforcement officers in the U.S. can operate in two modes: a drive-stun mode and a probe mode. In both modes, CEDs work by sending energy down two electrical contacts. If the contacts are touching an object, a conduit, the electricity will flow from one contact to the other through that object, closing the circuit.
An open circuit (when there is no conduit) on a CED can generate up to 50,000 volts (the peak open circuit arcing voltage). When the circuit is closed, such as when the probes are embedded in someone's torso, a CED may produce approximately 5,000 volts (the amount will depend on the model). For comparison, the standard U.S. wall outlet generates 120 volts. It is, of course, extremely dangerous to receive a shock from a wall outlet. So, how is it possible for a human body to safely receive 5,000 volts from a CED?
To answer that question, we need to look at another measure of energy: current. If we think of electricity as water flowing through a pipe, rather than electrons traveling along a wire, then voltage is the pressure it takes to push water through the pipe, while current is the rate at which the water flows. Electrical outlets have a high, continuous current — after all, we expect them to supply us with a high, steady stream of energy so our lights, appliances and electronics work without interruption.
CEDs, on the other hand, have a low, pulsed current. After the probes are attached to skin or clothing, the trigger activates a five-second series of low-current pulses. It may, for example, activate 19 low-current pulses per second that last for 30 microseconds (30 millionths of a second) each. It should be noted that some versions of CEDs in use can deliver multiple discharges if the trigger is pressed again after the first cycle or prolonged and uninterrupted discharges if the trigger is held down continuously.
CEDs will have different effects on people depending on which mode they are in and officers may use them for different purposes (incapacitation versus deterrence).
In probe mode, CEDs use compressed nitrogen to fire two barbed probes (sometimes called darts) at a target, imbedding themselves in the target's skin or clothing. Unlike in drive-stun mode, the probes are not directly next to one another and the electrical current is spread out across more tissue. When the trigger is pulled, electricity travels along thin wires attached to the probes. In addition to causing pain, the electrical current interferes with the target's neuromuscular system. The interference causes involuntary muscle contractions, temporarily incapacitating the target and making him or her easier to arrest or subdue.
In drive-stun mode, when a CED's contacts are applied directly to a target, CEDs do not have the same incapacitating effect that they usually do in probe mode. Because the electrical contacts are closer together, they do not engage or electrically excite as much tissue and, consequently, do not temporarily interfere with a person's neuromuscular system. They do, however, cause pain, which may deter an individual from continuing his or her behavior.
About This Article
This article appeared in NIJ Journal Issue 268, October 2011, as a sidebar to the article Final Findings From the Expert Panel on the Safety of Conducted Energy Devices by Brian Higgins.