Less-Lethal Force: Constitutional Limits, Deployment, and Liability

Less-lethal weapons are the intermediate force tools police use to control dangerous people without resorting to firearms: conducted energy devices, chemical sprays, impact projectiles, batons, and long-range acoustic devices. The name is deliberate. Every weapon in this category has caused serious injuries and deaths, so the policies and constitutional rules governing when officers may use them matter as much as the hardware. The sections below cover what these weapons are, how they work, when the law allows their use, and what officers and agencies face when a deployment goes wrong.

Where These Tools Fit in a Use-of-Force Response

Most agencies organize their options along a use-of-force continuum. The framework moves from officer presence and verbal commands, through hands-on physical control, then to less-lethal tools, and finally to deadly force. Officers are trained to match their response to the threat, and the level of force is supposed to decrease as the threat decreases.¹

Less-lethal weapons sit near the top of the ladder, one step below deadly force. That placement reflects reality. These tools carry real medical risks, and deploying them requires legal justification well beyond what is needed for a verbal command or a wrist lock. Many agencies have moved from a strict ladder to a decision-making model that emphasizes flexibility, but the underlying principle is the same: force must be proportional to the threat.

The Main Categories and Their Risks

Conducted Energy Devices

Conducted energy devices deliver a high-voltage, low-amperage electrical pulse that overrides the body’s motor signals and causes involuntary muscle contractions. The person loses voluntary muscle control for the duration of the cycle. Most models fire probes at a distance; many also have a close-range contact “drive stun” mode used for pain compliance.

The medical risks are more serious than early marketing suggested. Research published in the American Heart Association’s journal Circulation found that these devices can cause cardiac capture and, in some cases, ventricular fibrillation when probes land across the chest. Hundreds of deaths following conducted energy device use have been documented, and one manufacturer’s own estimate placed the cardiac arrest risk at roughly 1 in 100,000 applications. The risk rises when the subject has a pre-existing heart condition, a pacemaker, or when probes land directly over the heart.²

Chemical Agents

Oleoresin capsicum (pepper spray) and CS gas target the eyes, respiratory system, and mucous membranes, causing temporary blindness, coughing, and intense burning. Handheld sprays are built for single-subject encounters; grenades and canisters disperse irritants across larger areas for crowd situations.³

Decontamination is straightforward but essential: fresh air and flushing with cold water. Chemical decontamination agents should not be used, because they can worsen the reaction. Exposed subjects need monitoring to ensure breathing is not impaired, especially people with asthma or other respiratory conditions.

Impact Projectiles

Bean bag rounds, foam-tipped bullets, and rubber batons fire from specialized launchers. The idea is a painful strike from a safe distance without penetration. In practice the safety margin depends heavily on range and shot placement. A systematic review covering nearly 2,000 people struck by impact projectiles found 53 deaths and 300 cases of permanent disability. Head and neck strikes accounted for half of all deaths and over 80% of permanent disabilities, and ocular injuries resulted in permanent blindness more than 84% of the time.⁴

Safe firing distances vary by weapon and manufacturer, and the research shows they are poorly validated. Officers are instructed to aim at large muscle groups in the lower body, but close-range deployment and inaccuracy at longer distances both contribute to serious injuries. A round aimed at the thigh from a proper distance is a compliance tool. The same round striking the head at close range is potentially lethal.

Blunt Force Instruments

Expandable batons are the oldest category. They work through direct strikes or joint manipulation, typically targeting large muscle groups to cause pain and temporary immobilization. Policies classify strikes by target area: green zones (large muscles of the legs and arms) carry lower injury risk, while red zones (head, neck, spine, kidneys) are restricted to situations where deadly force would otherwise be justified.

Acoustic Devices

Long-range acoustic devices amplify voice commands and can emit high-decibel warning tones. Some agencies use them primarily for communication during crowd events, barricaded-suspect situations, and emergency management. The warning tone function raises distinct concerns about hearing damage. Policies that authorize these devices set minimum distances for unprotected bystanders and limit the duration and frequency of warning tones. Operators are expected to use the lowest effective volume and avoid deployment near people with hearing sensitivities, young children, or individuals experiencing a mental health crisis.

The Constitutional Rules That Govern Deployment

Graham v. Connor and Objective Reasonableness

The Fourth Amendment’s prohibition on unreasonable seizures provides the primary constitutional framework for any force used during an arrest or investigative stop. In Graham v. Connor, the Supreme Court held that force must be judged by an “objective reasonableness” standard, viewed from the perspective of a reasonable officer on the scene rather than with the benefit of hindsight.⁵

The Court identified three factors that guide the analysis:

The severity of the crime at issue.
Whether the subject poses an immediate threat to officers or bystanders.
Whether the person is actively resisting arrest or attempting to flee.

These are not a checklist with automatic answers. Courts weigh them against the totality of the circumstances, and the calculus shifts as the situation changes. An officer who uses a conducted energy device on someone swinging a pipe at bystanders faces a very different legal evaluation than one who deploys the same device on a person sitting passively on a curb.

Tennessee v. Garner and Fleeing Suspects

A separate line of analysis applies when force is used to prevent escape. In Tennessee v. Garner, the Supreme Court held that deadly force may not be used against a fleeing suspect unless the officer has probable cause to believe the suspect poses a significant threat of death or serious physical injury to others.⁶

Although Garner specifically addresses deadly force, its logic influences how courts evaluate less-lethal deployments against fleeing individuals. Deploying a conducted energy device against someone running from a traffic stop creates a foreseeable risk of serious injury from an uncontrolled fall. Courts have found that this kind of force against a non-violent suspect can be constitutionally excessive, even though the weapon itself is classified as less-lethal.⁷

Force Against People Already in Custody

Graham’s standard applies to people encountered on the street during arrests and investigative stops. A different standard governs force used against pretrial detainees in jails and holding facilities. The Supreme Court held in Kingsley v. Hendrickson (2015) that pretrial detainees challenging the use of force need only prove the force was objectively unreasonable under the Fourteenth Amendment’s due process clause. They do not need to prove the officer had a subjective intent to harm. For convicted prisoners, the Eighth Amendment’s cruel and unusual punishment standard applies, which is a harder bar to clear.

De-Escalation and Warnings Before Force

Modern use-of-force policy treats de-escalation as a core obligation, not an optional courtesy. The Department of Justice requires that officers be trained in techniques designed to gain voluntary compliance before using force, and that those techniques be employed whenever they would not increase the danger to the officer or others.⁸

De-escalation covers anything that stabilizes or slows a volatile encounter without physical force: creating distance, using calm verbal communication, calling for additional officers, or giving the person time and space to comply. Executive Order 14074, signed in 2022, requires all federal law enforcement agencies to adopt policies reflecting “principles of valuing and preserving human life” and to incorporate annual, evidence-based training consistent with the DOJ’s standards.⁹

Verbal warnings before deploying a less-lethal weapon are a related but distinct requirement. Federal policy requires officers to identify themselves and issue a verbal command to comply before applying force, when feasible. “Feasible” means a warning would not increase danger, allow escape, or lead to the destruction of evidence. When a warning is given, the officer should allow a reasonable opportunity to comply before following through.¹⁰

The warning requirement has teeth in court. Federal training materials note that using chemical spray or a conducted energy device as a pain compliance tool on a non-threatening person who simply refuses to cooperate, without first providing a warning and time to reconsider, has been found constitutionally excessive in prior cases.⁷

When Deployment Is Restricted

Dangerous Environments

Certain environments turn a less-lethal weapon into a lethal one. Using a conducted energy device on someone standing on a ledge, roof, or bridge creates an obvious fall risk. The same is true for people in water, on stairs, near glass, or holding sharp objects. Agency policies restrict deployment in these conditions because the neuromuscular incapacitation that makes the device effective also eliminates the person’s ability to catch themselves. Courts have held that the law is clearly established when a force option creates a foreseeable risk of death or serious injury from the surrounding environment.⁷

Vulnerable People

International policing standards require special consideration when force is used against people particularly vulnerable to harm: children, pregnant women, the elderly, individuals with disabilities, people experiencing a mental health crisis, and those under the influence of drugs or alcohol. A conducted energy device causes involuntary muscle contractions that pose a greater musculoskeletal injury risk to elderly individuals, and the tissue-penetrating probes are more dangerous for children and very thin adults because their body wall provides less protection from internal injury.¹¹

Agencies that encounter vulnerable populations regularly are expected to provide detailed training on identifying risk factors and de-escalating encounters before weapons enter the picture. The standard less-lethal playbook can cause disproportionate harm when applied to someone in psychiatric crisis, a frail elderly subject, or a juvenile.

What Has To Happen After a Deployment

Once a less-lethal weapon has been used, the person on the receiving end needs medical attention. This is a policy obligation, not a suggestion, and it applies whether or not the subject appears injured.

Conducted energy device probes embedded in skin should be removed by trained medical personnel. Probes in sensitive areas like the eyes, neck, face, or groin are handled exclusively in an emergency department. All subjects who have been exposed to a conducted energy device should receive a full medical evaluation.

Chemical agent decontamination requires fresh air and flushing with cold water. Subjects must stay under continuous supervision to ensure breathing is not impaired, and they should be paired with a trained responder who can render first aid if the reaction worsens. Delays in decontamination extend the suffering and increase the risk of respiratory complications.

Impact projectile injuries deserve particular attention because the damage is not always visible. A bean bag round to the abdomen can cause internal bleeding without an obvious external wound. Any subject struck by a kinetic projectile should be evaluated for internal injuries, not just surface bruising.

Documentation follows. Every less-lethal deployment triggers a mandatory use-of-force report, typically due before the end of the officer’s shift, documenting the time, location, reason for the encounter, the subject’s behavior, the weapon used, and the outcome. Supervisors review the report against radio logs and video evidence. If the narrative does not match the objective evidence, the report gets sent back for correction or escalated for investigation.

The FBI operates a National Use-of-Force Data Collection program for incidents involving a death, serious bodily injury, or the discharge of a firearm at or in the direction of a person. Participation is voluntary for state and local agencies. Executive Order 14074 made monthly reporting mandatory for all federal law enforcement agencies.¹²⁹

Civil and Criminal Liability When Force Is Excessive

Civil Lawsuits Under Section 1983

When a less-lethal deployment violates someone’s constitutional rights, the person harmed can sue under 42 U.S.C. § 1983. The plaintiff must show that the officer was acting in an official government capacity and that the officer’s actions deprived them of a right secured by the Constitution. If those elements are met, the officer and potentially the employing agency face liability for damages.¹³

The most common scenario involves deploying a less-lethal weapon against someone who posed no real threat, or continuing to use force after the person has already been subdued. Using a conducted energy device on a compliant individual, spraying a restrained person in the face with pepper spray, or firing impact projectiles at a peaceful crowd all create serious exposure. These cases are evaluated under the Graham reasonableness framework, and outcomes turn on whether the force was proportional to the threat at the moment it was used.

Federal Criminal Prosecution

Officers who willfully use excessive force can also face federal criminal charges under 18 U.S.C. § 242, which prohibits depriving anyone of their constitutional rights while acting under government authority. Penalties scale with the harm: up to one year in prison for the base offense, up to ten years if the victim suffers bodily injury or the officer used a dangerous weapon, and up to life imprisonment if the victim dies.¹⁴

Federal criminal prosecution requires proof of willful intent, which sets a higher bar than the civil standard. Prosecutors must show the officer deliberately chose to use force they knew was unconstitutional, not merely that a reasonable officer would have acted differently. Federal charges tend to follow the most egregious cases rather than borderline judgment calls.

Qualified Immunity

Officers facing civil lawsuits frequently invoke qualified immunity, a doctrine that shields government officials from personal liability unless they violated a “clearly established” constitutional right. Courts apply a two-part test: whether the officer’s conduct violated a constitutional right, and whether that right was sufficiently clear at the time that any reasonable officer would have known their actions were unlawful.⁷

Less-lethal weapons create a recurring problem with the “clearly established” prong. Because these technologies are relatively new and evolving, courts sometimes find that even when force was excessive, the specific legal question had not been settled enough for the officer to know that. One federal appellate court found that an officer who tased a pregnant woman three times in under a minute used excessive force, yet still granted qualified immunity because the law on that exact scenario was not sufficiently clear when it happened. New types of less-lethal force can exist in a legal gray zone until enough court decisions accumulate to make the constitutional boundaries obvious.

Pattern-or-Practice Investigations

When individual lawsuits reveal a broader problem, the federal government has a separate enforcement tool. Under 34 U.S.C. § 12601, the Attorney General can investigate any law enforcement agency suspected of engaging in a pattern or practice of conduct that deprives people of their constitutional rights. If the investigation confirms systemic violations, the DOJ can file a civil action seeking court-ordered reforms.¹⁵

These investigations often result in consent decrees that require the agency to overhaul its policies, training, data practices, and oversight mechanisms. Progress is measured through independent monitor reports and audits. Agencies that end up under consent decrees almost always share common failures: poor documentation, inadequate training, no meaningful internal review, and a pattern of complaints that leadership ignored.

1
National Institute of Justice. The Use-of-Force Continuum
2
American Heart Association. TASER Electronic Control Devices Can Cause Cardiac Arrest in Humans
3
StatPearls. Tear Gas and Pepper Spray Toxicity
4
PubMed Central. Death, Injury and Disability From Kinetic Impact Projectiles in Crowd-Control Settings
5
Justia. Graham v. Connor, 490 U.S. 386 (1989)
6
Justia. Tennessee v. Garner, 471 U.S. 1 (1985)
7
Federal Law Enforcement Training Centers. Qualified Immunity
8
U.S. Department of Justice. Department of Justice Policy on Use of Force
9
GovInfo. Executive Order 14074 – Advancing Effective, Accountable Policing
10
U.S. Department of Homeland Security. Department Policy on the Use of Force
11
Office of the United Nations High Commissioner for Human Rights. Guidance on Less-Lethal Weapons in Law Enforcement
12
Federal Bureau of Investigation. National Use-of-Force Data Collection
13
Office of the Law Revision Counsel. 42 U.S. Code 1983 – Civil Action for Deprivation of Rights
14
Office of the Law Revision Counsel. 18 U.S. Code 242 – Deprivation of Rights Under Color of Law
15
Office of the Law Revision Counsel. 34 U.S. Code 12601 – Cause of Action