In general, evidence of prior crimes or bad acts cannot be introduced at trial to prove that a person committed the crime for which they are currently charged. Under Minnesota Rule of Evidence 404(b), evidence of another crime, wrong, or act is not admissible to prove the character of the person or that the person acted in conformity with that character in committing an offense. The reasoning is that allowing evidence of a person’s prior bad acts will suggest that either that the person is prone to committing crimes or should be punished for his or her past indiscretions.
Evidence of prior crimes or bad acts may however, be admissible for other purposes, such as to show a motive, opportunity, intent, an identity, the absence of a mistake or accident, or a common scheme or plan. Named after the Minnesota Supreme Court case State v. Spreigl, such Spreigl evidence may only be admitted under certain conditions. First, the state must give notice of its intent to offer the evidence. Second, the state must clearly indicate what the evidence is being offered to prove. Third, there must be clear and convincing evidence that the defendant participated in the bad act. Fourth, the evidence must be relevant and material to the state’s case, meaning that the prior bad acts do not need to be identical to the crime charged, but must be sufficiently or substantially similar. Lastly, the probative value of the bad act evidence must not be outweighed by its potential for prejudice to the defendant. In other words, there has to be a balance between how useful the evidence is and how harmful it is to the defendant. If it is more harmful than helpful, it is most likely out. If it is close call, the court is supposed to exclude the evidence.
Therefore, if the state can show that something from years back is being used for an appropriate purpose, then it could be used against someone in a current case.