What is the test for determining whether a defendant is competent to stand trial?

"Due process requires that 'a person whose mental condition is such that he lacks the capacity to understand the nature and object of the proceedings against him, to consult with counsel, and to assist in preparing his defense may not be subjected to a trial.'" United States v. Arenburg, 605 F.3d 164, 168-69 (2d Cir. 2010) (quoting Drope v. Missouri, 420 U.S. 162, 171 (1975)). "Because this constitutional right spans the duration of a criminal proceeding, 'a trial court must always be alert to circumstances suggesting a change that would render the accused unable to meet the standards of competence to stand trial.'" Id. at 169 (citing Drope, 420 U.S. at 181) (emphasis in original).

We review for abuse of discretion a district court's determination not to hold a competency hearing. See United States v. Quintieri, 306 F.3d 1217, 1232-33 (2d Cir. 2002). "In deciding that an evidentiary hearing is unnecessary, a court may rely not only on psychiatrists' reports indicating competency but also on its own observations of the defendant." United States v. Nichols, 56 F.3d 403, 414 (2d Cir.1995).