When reviewing a district court's finding of competence, we inquire whether substantial evidence supports the district court's decision that the defendant was fit to proceed to trial. State v. McCarthy, 2004 MT 312, ¶ 20, 324 Mont. 1, 101 P.3d 288.
When sufficient doubt is raised as to an accused's competency to stand trial, the district court has a duty to sua sponte order a hearing on this issue. However, there can be no fixed or immutable signs which invariably indicate the need for further inquiry as inquiry into an accused's competency is necessarily based on the individual circumstances presented. State v. Garner, 2001 MT 222, ¶¶ 21, 23, 306 Mont. 462, 36 P.3d 346.
Courts have a continuing duty to review the issue of competency in criminal proceedings. State v. Bartlett, 271 Mont. 429, 433, 898 P.2d 98, 100 (1995).
The question of whether a doubt as to an accused's sanity is raised in any given case addresses itself directly to the sound judicial discretion of the trial court. But like any matter thus committed to the discretion of a court or its judge this discretion may not be exercised arbitrarily. State v. Kitchens, 129 Mont. 331, 339, 286 P.2d 1079, 1083 (1955).
Fitness to proceed to trial is a matter largely within the discretion of the District Court. Therefore, we will not overturn a decision of the District Court in the absence of a clear abuse of discretion. The evidence may conflict, but it is substantial if any reasonable trier of fact could rely upon the evidence in support of its conclusion. State v. Statczar, 228 Mont. 446, 457, 743 P.2d 606, 613 (1987).