In order to better understand the justice system and the parts where the law can be applied in a discretionary manner, it is important to first briefly provide an overview of the systems and balances aspect of law. As the flowchart shows, there are different segments of the system for the dispensation of justice. It is not enough that a perpetrator is apprehended.
There must also be an investigation and the findings must be presented before a judge and must be decided upon by a jury. This is only the initial part as the other parts include the corrections systems and the sentencing. As such, it is clear that at certain steps, discretionary power is granted to law enforcement officials and members of the Justice department in order for them to properly carry out their jobs.
Given this overview, the first area that must be pointed out is the entry into the system. The law provides a certain amount of latitude for law enforcement officials to decide whether or not a person was committing a crime or is suspected of committing a crime. While there are guidelines and rules that are used here such as probable cause, the determination of such can be said to be discretionary on the part of the officer. If the officer believes that there is a crime that has just been committed and that person is a suspect, he is allowed by law to apprehend the person even without a warrant. This is one area which may lead to the discretionary application of law.
Another important, and oftentimes overlooked part of the justice system, is the grant of pardon and clemency which is the power the president exercises. This is a power that is highly discretionary to the President and the President may exercise this power subject only to the right of review of the other co-equal branches of government. Since the sentencing system is an integral part of the Justice system, it stands to reason that any pardon or clemency given would result in the discretionary application of law since there would be no effective punishment.