Police discretion is the ability to choose a course of action because of broad limits of power. It "refers to the autonomy an officer has in choosing an appropriate course of action" (The Police In America, 113). It "includes authority to decide which of the various means of helping the helpless, maintaining order, and keeping the peace are best suited to particular circumstances" (www.worldandi.com/specialreport/1989/january/Sa15878.htm). The police need to have discretion since it is impossible to record everything on what they are supposed to do and not do. We can also understand that if you could record all the rules and regulations it would be too extensive for an individual to comprehend.
Looking at the criminal justice system as a whole, I find that the police officers are the ones who exercise the most discretion. They maintain the ability to enforce the law at anytime and anywhere, in uniform and out of uniform. For example, they are the ones who make the decisions regarding who they will pull over and who they will arrest. They must make a discretionary decision on what to do about a crime in progress if, for instance, they are out of uniform shopping with their family. There can be quite a number of important decisions facing them everyday, especially if they are not in their uniforms.
It is crucial for the police to use discretion because there may be new situations which arise that they have not run across yet. For example, let us just say that a police officer pulls over an individual who was speeding. This person may explain to the officer that his reason for speeding was some kind of an emergency situation that maybe he/she never heard of before. The officer, using his/her discretion, possibly might not issue that individual a summons. On the other hand, if this officer were to pull over someone in a non-emergency situation, such as joyriding, he/she would most likely issue that person a summons.