Probable Cause

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By: G. Cantor, La Mesa P.D. Sergeant (Ret)
Every police officer who comes out of a police academy understands the concept of "probable cause." Many who come in contact with the police do not understand it. The purpose of this article is to provide some insight as to what a police officer knows about it and how it is used.

"Probable cause" means it is probable that a violation of the law has occurred, is occurring or is about to occur. Strictly speaking, it is a standard of measure of provability of a fact, and that fact is a past, present or future occurrence of a crime.

There are some other standards of measure for proving a fact, so in order to grasp the concept of probable cause or "PC" as it is most often referred to, it is good to know what the other standards are.

The most difficult standard in law to prove is "Proof beyond a reasonable doubt." This is the standard that is required in a criminal court for the court to convict someone of a crime. "Proof beyond a reasonable doubt" is not "proof beyond any possible doubt," a common misconception. If a person is arrested for DUI, it will be the requirement of the prosecution to prove beyond a reasonable doubt that the person drove a vehicle while under the influence of alcohol.

The second most difficult standard is "preponderance of the evidence." This is a standard that is used in juvenile cases and civil cases. It simply means that one side has proven its side better than the other side, like a balance scale.

Because we live in the United States of America, we as citizens have a right to go about our business without unreasonable interference by the government. If the police were allowed to stop and interrogate simply on a whim or a hunch, our society would tend toward being a police state. On the other hand, if police were not allowed to stop citizens at all, we would move toward a state of anarchy. The courts, through their interpretation of the Constitution, recognize the need for a balance in government interaction with the public. Proving a crime beyond a reasonable doubt before a stop is made is unreasonable; therefore, the standard used to allow this interaction, other than a consensual contact, is probable cause.

For a police officer working the street, the easiest way to have probable cause to stop someone is some type of violation of a traffic law. As you know, there are a myriad of moving violations, registration violations and equipment violations in the Vehicle Code. Where as all of these requirements are necessary for the streets to be safe, the secondary benefit to the police officer is it provides countless ways of justifying a stop.

Once a stop is justified and made, if the officer goes beyond the primary purpose of the stop, his actions have to be justified based on probable cause to believe that there is an additional crime that has to be investigated. For example, if a police officer stops someone for speeding, removing the person from the car and doing a pat down search would be unjustified because the purpose of the speeding stop can be met by simply writing a citation. However, if during the stop something happens, or evidence of an additional crime comes to light that was not originally noticed, the officer can probe deeper because he has more probable cause.

Keep in mind, there does not have to be an actual violation of a crime as you might see in a traffic violation, only the probability of a violation. If a police officer sees a person driving during late hours of the night or early morning hours and sees the person weaving back and forth in the lane, or perhaps is driving too slow or the officer sees some other unusual driving pattern that appears to be suspicious, the officer can justify a stop simply for suspecting the person of being a drunk driver. If a stop is made under those circumstances, the suspicion that the person is a drunk driver has to be developed before the stop is made, not after.

If you are in the habit of taking a few drinks then driving, you may not be in favor of this lower standard called "probable cause," but for all of those who are responsible in their drinking and driving they can take comfort in the fact that it keeps the streets safer for all of us.

Greg Cantor Retired La Mesa Police Sergeant