Question: Under Garner, do we need to warn a barricaded suspect before we are going to deploy tear gas?
Answer: The foundation of warning an offender before the use of deadly force is the 1985 case of Tennessee v. Garner. This decision addressed the use of deadly force against fleeing felony offenders, and the court considered giving warnings, but didn’t make it mandatory. Specifically: “Thus, if the suspect threatens the officer with a weapon or there is probable cause to believe that he has committed a crime involving the infliction or threatened infliction of serious physical harm, deadly force may be used if necessary to prevent escape, and if, where feasible, some warning has been given.”
Feasibility must be based on the considerations of the officer on scene.
There's no legal requirement that an officer allow a violent offender to gain a deadly advantage, whereby a verbal warning exposes the officer to greater dangers by allowing the offender to target the officer or others on scene. Telling the suspect, you are going to use tear gas increases the chances he will prepare physically (putting on gas mask) and/or psychologically (getting ready for the pain).
I haven’t seen a policy that mandates a verbal warning in all matters of police use of force. There are no courts that have ruled you need to tell someone you are going to use non-lethal chemical agents (tear gas). The court in Tennessee v. Garner did not say what the verbal warning should be. Many agencies use the warning that they are going to use force and the suspect maybe injured. That seems to comply with Tennessee v. Garner.
