Can a defendant’s past crime be introduced into evidence?

A common question asked by criminal defendants with histories of prior criminal activity is whether evidence of a prior crime can be used to prove guilt. For example, a person who is accused of felony drug charges may have been convicted of a similar crime on a prior occasion. Can that earlier conviction be used to prove that the defendant committed the crime for which he or she is being tried?

The answer lies in the Massachusetts Guide to Evidence, a compilation of the law of evidence in the

Commonwealth as it has developed over time. Rule 404 deals with “Character Evidence” and “Crimes or Other Acts.” The general rule, applicable in both civil and criminal cases, is that a person’s character is inadmissible to prove that a person acted consistently with a specific character trait on the occasion in question. The same general rule applies to evidence of past crimes or other wrong acts. Evidence of a past crime is not admissible to prove the existence of a specific character trait and that the defendant acted in accordance with that trait.

Evidence of a past crime may be admissible for other purposes, such as proving that the defendant had a motive, purpose, opportunity or intent to commit the crime at issue. Such evidence can also be admitted to prove knowledge, identity or absence of mistake. The evidence of a past crime offered for any of these purposes must be excluded if, in the opinion of the judge, the probative value of the evidence is outweighed by the risk of unfair prejudice. Also, evidence of a past act is inadmissible if the defendant was tried and acquitted of the crime.

A careful criminal defense attorney can use the Massachusetts Guide to Evidence to ensure that prejudicial and irrelevant evidence is kept out of the trial. Knowledge of the principles of evidence and their proper application is one of the hallmarks of an effective defense attorney.

Source: Massachusetts Guide to Evidence, “Sec. 404. Character Evidence; Crimes or other Acts,” accessed on Nov. 25, 2017