The Niqab and the role of a witness in court
The judge's concern is a legitimate one. A jury should be able to observe the facial expressions of a witness. Indeed, facial expressions often convey much more than the spoken word.
On the other hand, the Koran ordains modesty in dress:
"Tell the faithful women to lower their gaze and guard their private parts and not display their beauty except what is apparent of it, and to extend their scarf to cover their bosom". Koran, 24:31
There are strong differences of opinion as to what this requires. Moderate muslims take the view that the niqab is not required, and that all the Koran stipulates is that a woman wear modest dress, covering her arms, legs and head. Such requirements of modesty in theory apply also to men, though in Marjane Satrapi's Persepolis (an enthralling, engagingly human graphic novel and film about life in post-revolutionary Iran) the character of Marji complains of double-standards for men and women, with men being able to sport tight clothing, while women are required to dress in full black hijab, being careful to avoid accentuating any body parts.