What is the test for determining whether a defendant's first reaction to security measures at trial is prejudicial?

In Holbrook v. Flynn, supra, 475 U.S. 560, 106 S.Ct. 1340, 89 L.Ed.2d 525, the high court opted for a case-by-case consideration of whether challenged security measures are so inherently prejudicial as to deny the defendant the constitutional right to a fair trial. The court recognized that jurors' initial reaction at the outset of a trial is not dispositive as the jurors may not be aware of the impact the practice will have on their attitude toward the accused. Therefore, the court must determine only whether the security practice or practices presented an "unacceptable risk" that impermissible factors will come into play. (Id. at p. 570, 106 S.Ct. 1340.) The court should look "at the scene presented to jurors and determine whether what they saw was so inherently prejudicial as to pose an unacceptable threat to defendant's right to a fair trial; if the challenged practice is not found inherently prejudicial and if the defendant fails to show actual prejudice, the inquiry is over." (Id. at p. 572, 106 S.Ct. 1340.)