"In December, 2012, the court ruled that in some cases, witnesses can wear a niqab while testifying, leaving it to trial judges to decide in individual cases. The following year, Justice Norris Weisman of the Ontario Court of Justice gave priority to the potential negative consequences for the accused if she didn’t bare her face.

“On a broader societal level, should the niqab impede effective cross-examination of the complainant by the accused’s counsel, they will not be able to assess the witness’s demeanour and tailor the thrust and direction of their questions accordingly,” Judge Weisman noted in his ruling. “Wrongful convictions could ensue with resulting loss of public confidence in the justice system.”

http://nationalpost.com/news/canada/toronto-woman-who-lost-fight-to-wear-niqab-in-court-disillusioned-after-crown-drops-sex-assault-case