What is the test for determining whether a trial court's decision to restrain a defendant violates federal due process rights?

Federal courts in California apply a similar "compelling circumstances" standard for determining whether a trial court's decision to restrain a defendant violates federal due process rights. (Castillo v. Stainer (9th Cir. 1992) 983 F.2d 145, 147.) Under the federal standard, a state trial court must assess the "limitations" presented by the use of shackles, including reversal of the presumption of innocence, impairment of the defendant's mental ability, impeding communication between the defendant and his counsel, detraction from the decorum of the trial, and pain. (Ibid.) "'After considering these factors, the trial judge "must weigh the benefit and burdens of shackling against other possible alternatives."' [Citations.]" (Ibid.) Where the jury does not see a defendant's restraint, any error in ordering the restraint is harmless beyond a reasonable doubt. (Id. at p. 149.)