In Colorado criminal trials, the prosecution is generally prohibited from presenting evidence of a Defendant’s prior bad acts. For example, a Defendant is charged with committing assault on Jan 1, 2023. The Defendant assaulted a different person on July 4, 2015. The prosecution cannot admit evidence of the 2015 assault to prove the Defendant has a character for committing assault, and therefore, he is more likely to have committed the 2023 assault. This is commonly known as “character evidence.” Colorado Rules of Evidence 404(a).
However, Colorado Rules of Evidence 404(b) states that evidence of a person’s other acts may be admissible as proof of the following: (1) motive, (2) opportunity, (3) intent, (4) preparation, (5) plan, (6) knowledge, (7) identity, (8) absence of mistake or accident, and (9) for other relevant purposes. This is commonly known as “404(b) evidence.” 404(b) evidence must be logically relevant to a fact at issue other than the character of the person who committed the other acts. Its probative value must not be substantially outweighed by the danger of unfair prejudice. Before presenting 404(b) evidence, the prosecution must obtain the Court’s permission. The prosecution may file a motion before trial requesting permission, or they may request during trial by making an oral motion outside the presence of the jury.
When used by the prosecution, 404(b) evidence can be extremely damaging to the Defendant’s chances of being acquitted by the jury. A skilled and experienced defense attorney can prevent the prosecution from admitting 404(b) evidence and thereby increase the likelihood of acquittal.