What is the test for relying on oral evidence in a personal injury case?

'The rule in cases such as the one before us is that the court must view the transaction with the 'most scrutinizing jealousy.' This means, of course, any court in which the issue may be raised. Oral evidence, of which there is not satisfactory independent corroboration, is the weakest kind of evidence known to the law. In Smellie v. Southern Pac. Co., 212 Cal. 540, 299 Pac. 529, 537, this court, in considering the same kind of evidence upon which plaintiff must rely in the instant case, said: 'Evidence of the declarations or oral admissions of a party are always received with caution. Code Civ.Proc., 2061, subd. 4. * * *