The standard of proof is exactly the same for law enforcement officers as it is for every other person investigated for potential criminal conduct. That is, the prosecution must prove, and a unanimous jury of twelve members must agree, that the individual charged is guilty beyond a reasonable doubt. This presumption of innocence and the proof beyond a reasonable doubt standard are fundamentally rooted concepts in the American system of law.
Uniform Crime Charging Standards mandate that prosecutors file charges only when, after a thorough consideration of all pertinent data, there is a reasonable likelihood of conviction by an objective factfinder weighing the admissible evidence, including the most plausible and reasonably foreseeable defense that could be raised at trial. Evidence that the prosecutor knows will be inadmissible at trial under the California Evidence Code should not be considered in this determination. The charging mandate described above is equally applicable to the lowest of criminal offenses as it is to the most heinous.
We cannot simply charge a person with a criminal offense when there is insufficient evidence to do so and then let a jury sort out whether he/she should be convicted. Under the law and our code of ethics, we must be sufficiently convinced that a unanimous jury would find that a crime was committed by the person before we can file charges.