Last Thursday, the California Supreme Court ruled that positioning a uniformed deputy next to a testifying criminal defendant isn't inherently prejudicial. Justice Carol Corrigan wrote that "jurors may view the sight of an officer accompanying the defendant to the witness stand as nothing more than a routine measure." On the dissent, Justice Carlos Moreno, joined by Justice Joyce Kennard, said that such an act posed a "serious risk" to an individual's right to a fair trial.
This case occurred in Alameda County, when the trial judge directed a deputy to stand at a defendant's side as he testified on his own behalf in a rape trial. The defense argued that this was akin to a "human shackle" unjustified by good cause. Nonetheless, the majority of the Court held that the presence of a deputy "does not directly impair the accused's mobility, nor does it create the affront to human dignity that we have lamented in the context of visible shackles."
The ruling is at: People v. Stevens, 09 C.D.O.S. 13508.