The compelling state interest here is a fair trial for someone accused of murder.
In that case, remove the American flag, eliminate the ‘swearing to tell the truth under God’ and have everyone in the courtroom naked to ensure that there are no prejudicial facts, er, evidence that could sway the jury.
Proving that a display of ashes endangers a fair trial would be the point here , or, at the very least, clearly inferring such, before a claim of compelling state interest can be established. Again, the judge absolutely abridged the attorney’s First Amendment right on the basis that practicing his Faith somehow in some yet to be determined manner MAY have adversely affected the trial. MAY does not trump ABSOLUTE.