I would like to start off by acknowledging a shocking revelation. Police officers are human beings. We have feelings and emotions. We actually do care what happens to the people that live in the communities in which we work. Almost all the calls that we respond to are emotional to some degree. A mother and father lost their son in a car wreck. A person is drunk and angry over losing a job and had beat up his wife. A child is sexually abused by an uncle. Whatever the situation, a police officer has to cope with other people's emotions while keeping his emotions in check. This can really be tough at times. There are several factors that can lead an officer to lose control and overreact.
Police officers are allowed to feel anger, sadness, fear, elation, and all the other emotions we as human beings feel. Police officers, however, are not allowed to become abusive, either verbally or physically. Police officers are required to keep their emotional responses in the realm of acceptable behavior. No one should ever have to be subjected to belittlement, cursing, or unnecessary physical injury from an out of control officer. We often see images on television, the internet, or the newspapers of police officers crossing the line.
It is a rare police officer that goes to work with the goal of finding and "putting the hurt on" someone during the shift. So, what happens to police officers that cause them to cross the line of acceptable behavior? There are numerous combinations of factors that can lead to abusive and/or excessive force events. The most common factors include: fear and anger, improper training, lack of experience, problems at home, problems at work, taking things said or done out on the street personally, stress, and steroid, drug, or alcohol abuse.
The two emotions that are the most likely to cause problems between police officers and the public are fear and anger. Fear can be characterized as an emotional or stress response to a situation that affects our survival. As a natural automatic response, we will either fight the attacker or flee. This is known as the "Fight or Flight" response. This response is genetically programmed into our being. When this response is triggered, our bodies go through a rapid physical and psychological change. The change prepares us to move faster, be more alert, have sharper vision, and raises our ability to endure pain, all to better defend ourselves or escape the attack. Anger is similar to fear in that they both have the same types of physical and psychological changes. Anger is different, however, because it is a response that prepares us to attack, not defend or escape. Attack in this context is to either get mad and take action to right a wrong in a non-aggressive manner, or take an aggressive verbal or physical action.
As you can see, fear and anger are natural, engrained, behaviors. The goal of police departments is to properly vet applicants to eliminate the ones that have trouble controlling these behaviors. The people that are hired are then conditioned through training to deal with fear and anger in an acceptable and predictable manner. The use of proper and repetitive training techniques in apprehension and self-defense builds muscle and mental memory for the body to draw on in high stress situations. Training also addresses the legal limits of acceptable force through tools like a Use of Force Continuum chart. The ultimate goal is to minimize injuries to the officer and lower the chances of an excessive use of force situation.
The next factor is the lack of experience. When I refer to the lack of experience, I am not referring to being a novice to police work. An overreaction due to lack of experience can occur anytime during an officer's career. This factor goes hand-in-hand with training. Training does provide a certain amount of experience, albeit, in a controlled setting. Obviously, officers with only a few years experience are maybe more likely to mishandle situations leading to an overreaction. Let me give you examples of what I mean by all this. A police officer with about a year on the job responds to a domestic dispute. He arrives at the door of the residence and sees a man standing over a woman lying on the ground. She is bleeding from her lip and nose. He immediately enters the residence, strikes the man on the leg with a baton, takes the man to the ground, and handcuffs him. The officer then finds out from the woman that her sister hit her and left the house. The man was not involved. The officer clearly jumped to conclusions, overreacted, and injured and arrested an innocent person. He did not have a proper perception of when a true threat was present. A more experienced officer would have taken a more measured approach to the situation. He would have approached with caution, and asked questions to determine what happened before taking action.
Police officers with many years on the job can also lack experience in certain types of situations that can lead to an overreaction. For example, a police officer is basically "retired" on duty, meaning he does as little as possible. He never makes arrests. He avoids stopping people on traffic that he thinks might cause him trouble. He tries to evade "hot calls". One night a fellow officer gets in a pursuit of a suspect in a stolen vehicle. He is the only officer available to back the pursuing officer. He tries to catch the pursuit. The suspect stops the car and flees on foot. The pursuing officer catches and handcuffs the suspect who is lying on the ground. The suspect is not resisting. He arrives on the scene. He is so pumped up and excited that he attacks the suspect. He kicks the suspect in the ribs several times. He pulls his gun and presses the barrel to the suspect's temple. He then curses and yells threats at the suspect. This is clearly an overreaction. This officer has avoided these types of calls for so long that he was not used to dealing with them. His training and work experience to deal with these situations occurred so far in his past that his mind no longer reverted to that training and experience to handle the situation. He reacted with uncontrolled anger.
The next factors deal with the influence of personal and work problems on how an officer reacts to situations in the field. The officer had a fight with his wife, or he failed to get promoted at work. There are an infinite number of things that can stress an officer to the point of affecting his work. It can be very easy for an officer to vent his frustrations and problems out on people he deals with in the public. This is especially true if the person is a criminal violator. The violator many times will choose to take the abuse to avoid additional charges like, interfering, resisting, or battery on an officer. Who is going to believe him over the police officer, anyway? An officer may get away with this a few times, but a pattern will burn him and probably hurt or end his career.
Taking things said or done out in the field personally probably gets more officers in trouble than anything else discussed in this article. Citizens and prisoners always have and always will verbally abuse and taunt police officers. They will also try and goad the police officers into striking them. It is a fact of life in this line of work. A police officer must develop a thick skin and learn not to take it personally. When it becomes personal, the officer loses control and the bad guys gain it. The ultimate result can be termination, criminal charges, and law suits.
Stress is nature's way of preparing us for action. Too much stress, however, can have a very negative effect on the body. Nervousness, irritability, anxiousness, and jumpiness all are results of stress. Stress can also interfere with our ability to fine tune our judgments or make good decisions. This is the root of the problem for police officers in the field. Police officers must learn to deal with stress if we are to survive to our retirement. There are four different ways to deal with stress. Exercise is a good way to burn off that negative stress. Three other ways to deal with stress are: to change the environment or situation that is causing the stress, change our interpretation or how we feel about what's causing the stress, or if no control is possible, learn to accept and survive the stressor. 
The final factor I will discuss deals with substance abuse. Police officers handle so many calls during their careers involving substance abuse, and see the consequences, that it seems odd how many police officers fall victim to it themselves. Most substances that are abused affect the mind's ability to function properly. Police officers must be alert and able to rationally observe signs of escalating tension on calls. The police officer's goal is to spot these signs and work to de-escalate the situation before it explodes into a violent encounter. Police officers also need to use their judgment to properly determine the amount of force used when events do become violent. If a police officer's judgment is impaired, so is his ability to gauge the level of force he should use. Many police departments have mandatory drug testing after a serious use of force incident to address this very issue.
Police officers have been in trouble for alcohol and any number of legal and illegal drugs. All of them greatly diminish an officer's ability to do his job. Anabolic steroid use, however, is the new problem for police departments. The biggest problem with anabolic steroids is that they can trigger sudden violent and irrational behavior. There have been several high profile news stories about police officers getting arrested or fired for steroid use. Almond, Michigan officer Craig Brown was arrested for selling anabolic steroids to an undercover officer. On August 9, 1997, Off. Volpe of the NYPD, as described by fellow officers, went on a "roid rage" and attacked Abner Louima with a broom stick in the police station. Off. Volpe sodomized him puncturing his colon and bladder. Off. Volpe had been purchasing the steroids from another NYPD officer by the name of Dols. Volpe was arrested. Dols was later murdered by his mafia suppliers because police officers stopped buying from him. In the fall of 2004, two Oklahoma officers were arrested and three were fired for selling or using anabolic steroids. Police officers often claim that they began using anabolic steroids to improve their abilities to handle violent subjects. The steroids make them stronger and more physically fit. The ironic thing about it is that they think it makes them better police officers. Instead, it makes them a ticking time bomb that could explode with huge repercussions.
Police officers deal with highly charged and emotional situations on a regular basis. We must strive to deal with the citizens of our communities in an honorable, restrained, and professional manner. It is okay to have feelings and to express them. We are not cold-blooded robots. We surely do not want our citizens to think so. We also do not want to be overly emotional to the point that we can no longer properly do our jobs. We especially want to avoid causing unnecessary and abusive harm to people in our communities. The best advice I can give is to stay well grounded in your community. Do not let police work overwhelm and consume your life. After all, there is more to life than work.
 The Fight or Flight Response, http://www.mindbodymed.com/EducationCenter/fight.html
 J. R. de Szigethy, http://www.americanmafia.com/Feature_Articles_11.html