Evidence of Incapacity Before and After

If the evidence shows incapacity before and after a date, there is an inference and "perhaps there is even a legal presumption" that the incapacity existed on the in-between date:

The evidence above recited is more than adequate to sustain the finding that decedent lacked testamentary capacity at the time the purported holographic will was executed. As stated In Re Estate of Fosselman, 48 Cal.2d 179, 185-186, 308 P.2d 336, 340: 'Testamentary incompetency on a given day, * * * may be proved by evidence of incompetency at times prior to and after the day in question. In re Estate of Perkins, supra, 195 Cal. 699, at page 703, 235 P. 45; In re Estate of Lingenfelter, supra, 38 Cal.2d at page 580, 241 P.2d 990; see Vitale v. Vitale, 147 Cal.App.2d 665, 669-670, 305 P.2d 690. Once it is shown that testamentary incompetency exists and that it is caused by a mental disorder of a general and continuous nature, the inference is reasonable, see In re Estate of Baker, 176 Cal. 430, 437-438, 168 P. 881; Vitale v. Vitale, supra, perhaps there is even a legal presumption (Code Civ.Proc., § 1963, subd. 32; see In re Estate of Schwartz, 67 Cal.App.2d 512, 521, 522, 155 P.2d 76; Byrne v. Fulkerson, 254 Mo. 97, 123, 162 S.W. 171; Bever v. Spangler, 93 Iowa 576, 601, 61 N.W. 1072, that the incompetency continues to exist.'

In re Wolf's Estate,(1959) 174 Cal.App.2d 144, 148. While the inference is not conclusive evidence of incapacity, it is substantial evidence:

There was direct and circumstantial evidence that decedent's mental condition had not materially changed in the interval between the execution of the purported holographic will and the appointment, less than a month later, of proponent as guardian of the person of decedent. Such an adjudication would not conclusively establish lack of testamentary capacity (In re Estate of Jamison, supra, 41 Cal.2d 1, 13, 256 P.2d 984; see In re Estate of Worrall, 53 Cal.App.2d 243, 247-248, 127 P.2d 593), but it would constitute substantial evidence on which a finding of testamentary incapacity may rest. Cf. In re Estate of Krause, 71 Cal.App.2d 719, 725, 163 P.2d 505.

Id., at p. 149.