Opening statements in criminal trials are regulated by Rule 24(a) of the Massachusetts Rules of Criminal Procedure.
Rule 24(a) gives both the prosecutor and the defense counsel 15 minutes to make an opening statement.
The prosecutor must present his statement first at the very beginning of the trial.
The defense counsel, however, may give his statement immediately after the prosecutor’s opening or at the end of the prosecutor’s case.
The opening statement is not intended for argument. Instead, its purpose is to allow both sides to outline their cases and the evidence they intend to present during the trial.
According to the notes for Rule 24(a):
An opening statement has a narrow purpose and scope. It is to state what evidence will be presented, to make it easier for the jurors to understand what is to follow, and to relate parts of the evidence and testimony to the whole; it is not an occasion for argument. To make statements which will not or cannot be supported by proof is, if it relates to significant elements of the case, professional misconduct. Moreover, it is fundamentally unfair to an opposing party to allow an attorney, with the standing and prestige inherent in being an officer of the court, to present to the jury statements not susceptible of proof but intended to influence the jury in reaching a verdict.
Lawyers who go outside the bounds and add irrelevant or prejudicial facts to their opening statements risk being sanctioned. See S.J.C. Rule 3:22A.