Probable cause and reasonable doubt are two very important concepts in criminal cases. But they relate to two different aspects of those cases. An officer must have probable cause to make an arrest. A prosecutor must prove a case beyond a reasonable doubt.
Probable cause exists if an officer has knowledge and trustworthy information sufficient to warrant a person of reasonable caution and prudence in believing that an arrestee has committed an offense. Probable cause may include information that an officer does not have first-hand knowledge of, such as witness statements. It may include knowledge based on the officer’s training and experience, for example what heroin looks like or how it is commonly packaged. An officer may obtain evidence by way of a search warrant: DNA, blood or cell phone records, for instance. It is important that if you are the subject of a criminal investigation to limit the evidence you provide to law enforcement as they seek to develop probable cause. Most often that means that if an officer asks for consent from you, such as for a search, or wishes to question you, the answer is no.
Proof beyond a reasonable doubt is a much tougher burden for the state than probable cause. The state must prove beyond any reasonable doubt that an individual committed an offense. That proof is provided to a judge or a jury during the course of a trial. The evidence must come directly from the individual with personal knowledge, in other words hearsay is not admissible. The State cannot prove that a substance is heroin based on an officer’s training and experience. The substance must be tested. The scientist who conducted the testing must testify. Evidence that is sufficient for probable cause for an arrest does not necessarily lead to a conviction.