A police officer is expected, and trained to, use his or her judgement during the course of every shift worked. Officers regularly encounter situations that require on-their-feet decisionmaking that is usually a product of experience and knowledge of human nature. They look for indicators that the driver of a car in front of them may be operated by someone who has been consuming alcoholic beverages, or that houses in the neighborhoods they patrol may used for nefarious purposes, for example, to manufacture or distribute illegal narcotics. And for every encounter resulting in an arrest, or assistance in an arrest or in the questioning of suspects or witnesses, they are required to file reports with their departments detailing their observations and actions. There is usually little room for supposition in these reports; the prosecutor reading the police officer's report wants facts, not opinions that can be manipulated during a trial by defense council.
Despite the requirement that police reports be as free of personal opinion as possible, there are instances when opinion is not only relevant, but extremely important. One such incident would involve a questionable use of lethal force by an officer in the line of duty. The facts may indicate a risk to the officer, or to an innocent bystander, to which the officer feels compelled to respond with lethal force. Unless there is clear evidence that the suspect was in fact threatening the life of the officer or of an innocent citizen, for example, through discharge of a firearm at the officer or citizen, or clearly pointing a weapon while acting in a manner consistent with the imminent discharge of such weapon by a suspect, then the officer's opinion or instincts become relevant. The officer may have to testify in a trial that he believed -- didn't know, but believed -- that his or her own life or that of an innocent citizen was in imminent danger. In such circumstances, the officer will put his or her opinion in the official report.
Another instance in which personal opinion may be used in a police report involves observation of a pattern of activity often consistent with the commitment of a crime, but for which only circumstantial evidence exists. The crime may not have occurred, but the officer, based upon his or her experience in law enforcement, may believe that an individual or group of individuals is preparing to commit a crime, and acts to prevent that crime by requesting a warrant to search a car, home, garage, or whatever the structure might be. Because no crime has been committed, the officer is operating on the basis of instincts, and that has to be reflected in the accompanying report. Criminal cases -- and conspiracy cases are usually difficult to prosecute -- that hinge on detection of patterns of activity normally associated with criminal behavior are, by nature, dependent upon opinions. In such instances, it is appropriate for an officer's opinion to be inserted into the report. It is ultimately up to the prosecutor's office to determine whether there is sufficient evidence to go to trial, but the whole notion of "probable cause" is an inherent part of the process by which searches are conducted, and probable cause can be a matter of opinion.