http://www.theguardian.com/law/2013/nov ... ken-clarke

There's any number of trials where witnesses give evidence from behind a screen, ranging from children to soldiers...

True. The difference is, the judge and court staff confirm the identity of the witness before they give evidence. As long as that is still the case with veiled witnesses, I don't see the problem.

I believe the quoted justification was that seeing a defendant's reaction to the questioning of witnesses is part of how the jury decide if they are guilty or innocent. So it's not just about identification, it's about body language Given that, it is against the interests of justice for the accused to be hidden be it by a nijab, balaclava, helmet or whatever. By that, a scarf would be acceptable - it's the face that's important.