When mail is inspected by a prison officer in a criminal case, is the mail of a defendant confidential?

When the mail is legal mail, there are heightened concerns with allowing prison officials unfettered discretion in opening and reading an inmate's mail. Prisoners have a Sixth Amendment right to confer privately with counsel and the practice of opening legal mail in the prisoner's presence is specifically designed to protect that right. Id. at 1196 (Sixth Amendment requires a pretrial detainee be present when legal mail related to a criminal matter is inspected; even a single incident of improper reading of a pretrial detainee's mail may give rise to a constitutional violation). "A criminal defendant's ability to communicate candidly and confidentially with his lawyer is essential to his defense." Id. at 1198 (quoting Nordstrom v. Ryan, 762 F.3d 903, 910 (9th Cir. 2014)).