CEDs have been purchased and used by law enforcement agencies over the last few decades as a "less-lethal weapon." CEDs have generally been used to stun and immobilize subjects, so officers will have less difficulty in subduing them when resistance occurs; however, CEDs have occasionally been linked to long-term physical handicaps and deaths. Although the effects of CEDs have been studied by medical researchers and defendants' rights group, scientific research has yet to produce conclusive evidence that CEDs, when used properly by trained officers, cause any lasting cognitive or physical damage to individuals who have no pre-existing physical handicaps. The emerging awareness of the danger of CED misuse brought the issue before federal courts to rule on constitutional standards for CED use. This trend culminated in the Fourth Circuit's 2016 decision in Armstrong v. Pinehurst, which held that CEDs are lawfully used only to counter an immediate danger to officers or others; specifically, these stun guns should not be used on a fleeing suspect. This appellate decision is binding federal law in North Carolina, South Carolina, Maryland, Virginia, and West Virginia. This "Armstrong" decision challenged police policies that allow the use of CEDs on subjects fleeing or even physically resisting police, but who pose no immediate danger to officers or others. Other courts have since adopted the "bright-line" rule that only a need to protect police or others from a present threat, and not just the desire to control the subject, can justify CED use.