Is a defendant required to be present at a hearing?

during criminal proceedings in not absolute, however: "[A] defendant is guaranteed the right to be present" at a particular stage of a criminal proceeding only if that stage "is critical to its outcome," and "his presence would contribute to the fairness of the procedure." Id. Thus, a defendant's presence is not constitutionally required "when [his] presence would be useless, or the benefit but a shadow." Snyder, 291 U.S. at 106-07 (collecting cases). See also United States v. Gagnon, 470 U.S. 522, 526-27 (1985) (identifying the key inquiry as whether the defendant's absence impaired his ability to defend himself against the charges).