Shooting to wound is an attempt to use a firearm to harm someone without killing them. It is controversial since the unpredictable nature of firearm wounds could result in the wound failing to incapacitate the target. It may also accidentally kill or miss the target, the latter presenting a risk of unintended casualties. Limbs are one main area often targeted when shooting to wound. However, limbs are smaller and can be moved faster and more radically than the torso, so the option of shooting to wound is generally viewed with skepticism by law enforcement in the United States. The usual policy in American law enforcement agencies is that any use of a firearm corresponds to deadly force on a use of force continuum. That is, if the subject presents an immediate threat to life, targeting extremities with a firearm is unlikely to stop the threat in time due to the high difficulty and low chance of incapacitation, while one who does not present an immediate threat should not be fired upon at all. Instead, policemen are trained to aim for the "center mass", as the aggressor is more likely to be hit and stopped.