The court had already ruled that the instruction should be given when “warranted by the evidence” and when the “witness and offender are of different races.”

“In criminal trials that commence after the issuance of this opinion, a cross-racial instruction should always be included when giving the model eyewitness identification instruction, unless the parties agree that there was no cross-racial identification,” the court ruled in an opinion written by Supreme Judicial Court Chief Justice Ralph Gants.

The state’s highest court ruled Thursday that judges must instruct jurors that eyewitnesses may have greater difficulty accurately identifying somone who is not their own race, unless both prosecution and defense agree that it’s not an issue.


But the court said it had not previously defined what evidence was necessary and who, if anyone, should decide whether the witness and the person identified were of different races.

Noting that the concept of race is “notoriously unclear,” the court settled on generally requiring the instruction, unless both sides agree it’s not part of the case.

“This obviates any need for the judge to decide whether the identification was actually cross-racial, or whether jurors might perceive it to be. If the jury receive such an instruction but do not think the identification was cross-racial, they may simply treat the instruction as irrelevant to their deliberations,” the court said.

The court, ruling in the case, Commonwealth v. Elvin Bastaldo, said that the “cross-race effect ... has reached a near consensus in the relevant scientific community and has been recognized by courts and scholars alike. We remain convinced that jurors who are asked to evaluate the accuracy of an identification should be informed” of the effect.