In what circumstances will a judge grant a motion of appeal in a probation revocation hearing?

In probation revocation hearings, where the ultimate decision is "predictive and subjective in nature," Black v. Romano, --- U.S ----, 105 S.Ct. 2254, 2259, 85 L.Ed.2d 636 (1985), and the sentencing court is granted broad discretion, United States v. Dane, 570 F.2d 840, 843 (9th Cir.1977), cert. denied, 436 U.S. 959, 98 S.Ct. 3075, 57 L.Ed.2d 1124 (1978), the first inquiry of an appellate court should be into the admissibility and sufficiency of the evidence actually relied upon by the trier of fact. Only if that evidence is deficient should the court ascertain whether other evidence might have supported revocation and whether a remand is necessary in order for the district court to exercise its discretion upon the basis of that additional evidence.