Suicide by police is a suicide method in which a suicidal individual deliberately behaves in a threatening manner, with intent to provoke a lethal response from a public safety or law enforcement officer.
There are two broad categories of "suicide by cop". The first is when someone has committed a crime and is being pursued by the police and decides that they would rather die than be arrested. These people may not otherwise be suicidal but may simply decide that life is not worth living if they are incarcerated and thus will provoke police to kill them. The second version involves people who are already contemplating suicide and who decide that provoking law enforcement into killing them is the best way to act on their desires. These individuals may commit a crime with the specific intention of provoking a law enforcement response.
The idea of committing suicide in this manner is based on trained procedures of law enforcement officers, specifically the policy on the use of deadly force. In jurisdictions where officials are readily capable of deadly force (often by being equipped with firearms), there are usually set circumstances where they will predictably use deadly force against a threat to themselves or others. This form of suicide functions by exploiting this trained reaction. The most common scenario is pointing a firearm at a police officer or an innocent person, which would reasonably provoke an officer to fire on them in defense. However, many variants exist; for example, attacking with a knife or other hand weapon, trying to run an officer or other person over with a car, or trying to trigger a (real or presumed) explosive device.
This entire concept hinges on the person's state of mind, and their desire to end their own life, which can be difficult to determine post mortem. Some cases are obvious, such as pointing an unloaded or non-functioning gun (such as a toy gun, air gun, airsoft gun or starter's pistol) at officers, or the presence of a suicide note. Some suspects brazenly announce their intention to die before they act (e.g., the iconic declaration "You'll never take me alive!"). However, many cases can be more difficult to determine, as some suspects with the desire to die will actually fire live ammunition and even kill people before being killed themselves. Many law enforcement training programs have added sections to specifically address handling these situations if officers suspect that the subject is attempting to goad them into using lethal force.