What is the appellate standard of review for a tort claim under section 946.6 of the California Tort Claims Act?

The determination of the trial court granting or denying a petition for relief under section 946.6 will not be disturbed on appeal except for an abuse of discretion. (Ebersol v. Cowan (1983) 35 Cal.3d 427, 435, 197 Cal.Rptr. 601, 673 P.2d 271.) However, the appellate standard of review in examining cases where the trial court has denied a petition for relief under the Tort Claims Act is more rigorous because the law favors the hearing of matters on their merits, rather than upholding a strict adherence to procedural doctrine. (County of Santa Clara v. Superior Court (1971) 4 Cal.3d 545, 552, 94 Cal.Rptr. 158, 483 P.2d 774.) In our view, where, as here, the only issue before the trial court is whether the public entity would be "prejudiced" within the meaning of section 946.6, subdivision (c)(1), an abuse of discretion will exist if the finding of the trial court is not supported by substantial evidence.