Generally defendants must be free from handcuffs or shackles during trial. The trial judge can, however, order the use of such restraints if they are justified.
According to the Supreme Judicial Court:
the Fifth and Fourteenth Amendments to the United States Constitution prohibit the use of physical restraints visible to the jury absent a trial court determination, in the exercise of its discretion, that they are justified by a State interest specific to a particular trial. Although a judge has discretion to order shackling for court room security, resort to such a measure must be case specific reflecting particular concerns related to the defendant on trial, and appropriate findings must be placed on the record at the time shackling is ordered. (Citations and quotations omitted.)
Commonwealth v. Rocheleau, 90 Mass. App. Ct. 634, 637 (2016).
The same SJC opinion states,
For a fair trial by an impartial jury shackling and other unusual security measures are of course to be avoided if possible. These displays tend to create prejudice in the minds of the jury by suggesting that a defendant is a bad and dangerous person whose guilt may be virtually assumed. Before a defendant may be tried in shackles, a judge should state the reasons in the presence of counsel and defendant and provide an opportunity for counsel to make their objections known, thereby making a record. (Citations and quotations omitted.)
Moreover, the trial judge can, if necessary, remove the defendant from the courtroom during trial.
A judge may direct that a defendant be removed from the courtroom during trial if the defendant’s behavior becomes so disruptive that the trial cannot proceed in an orderly manner. The judge shall make findings on the record describing the disruptive behavior and explaining how the trial cannot proceed in an orderly manner. At the request of the defendant, the judge shall instruct the jury that the defendant’s removal and absence are not to be considered by the jury.
Mass. Rules of Criminal Procedure Rule 45(a).
Some defense attorneys will even push for their clients to be free from courtroom holding cells during pretrial proceedings. And at least one federal court has shown itself favorable to the idea. See State of Washington v. Luthi, 549 P.3d 712, 720 (2024).