Attorneys may impeach a witness’s credibility during trial if the witness has a criminal record that fits the criteria of M.G.L. c. 233, Sec. 21.
That statute generally allows lawyers to use any of the following to impeach a witness:
- misdemeanor convictions less than five years old;
- felony convictions that were not punished by a state prison sentence and are less than ten years old.
- felony convictions that were punished by a state prison sentence and less than ten years has pasted since “the date of expiration of the minimum term of imprisonment imposed by the court.”
These dates may be extended if additional convictions occur during the five-to-ten year limitation period.
Additionally, it is within the discretion of the judge whether the witness’s prior convictions can be introduced at trial:
If a prior conviction is within the prescribed time limits of G. L. c. 233, s. 21, the decision whether to admit evidence of prior convictions to impeach a witness involves an exercise of discretion by the judge. The judge must balance the danger of unfair prejudice which can result from the admission of evidence of prior convictions against the probative value of the evidence for the purpose of impeachment. Generally, in order for the prejudicial effect to outweigh the probative value of prior conviction evidence, the “prior conviction must be substantially similar to the charged offense. (Citations and quotations omitted.)
Commonwealth v. Leftwich, 430 Mass. 865, 869 (2000).
The purpose of the evidence is not to show that the witness is a bad person. Rather, the evidence must be used to demonstrate that witness’s disregard for the law:
The theory underlying § 21 is that a witness’s earlier disregard for the law may suggest to the factfinder similar disregard for the courtroom oath. One who has been convicted of crime is presumed to be less worthy of belief than one who has not been so convicted. Thus, while we do not allow a witness to be impeached by evidence of prior bad acts, if those bad acts have resulted in a conviction, the conviction itself may be admissible under § 21.
Commonwealth v. Harris, 443 Mass. 714 (2005).
Finally, to impeach a witness by a criminal conviction, the conviction must be proved by a court record or a certified copy. See Commonwealth v. Puleio, 394 Mass. 101, 104 (1985).