Excessive force has never been taught. Has it been practiced? Of course! Sufficient force to overcome resistance is certainly taught, as it is both sound reasoning and should be common sense. Having said that, homicide is certainly committed by some police officers. Why? We will never know. Some of them were never fit to carry badge and gun. Others might have been under a load of stress, on drugs - prescription or otherwise. Either way, and no matter the cause, intentional homicide should net one a controlled environment for the amount of time that judge or jury decides.