What is the test for determining whether a plaintiff's predisposing physical condition was a contributory factor in his death?

In that situation, the law is clear: "[A]s long as the jury finds that without the criminal act the death would not have occurred when it did, it need not determine which of the concurrent causes was the principal or primary cause of death. Rather, it is required [only] that the cause was a substantial factor contributing to the result: "[N]o cause will receive judicial recognition if the part it played was so infinitesimal or so theoretical that it cannot properly be regarded as a substantial factor in bringing about the particular result." [Citations.] [] This is true even if the victim's preexisting physical condition also was a substantial factor causing death. [Citation.] So long as a victim's predisposing physical condition, regardless of its cause, is not the only substantial factor bringing about his death, that condition ... in no way destroys the [defendant's] criminal responsibility for the death. [Citations.]" ( People v. Catlin (2001) 26 Cal.4th 81, 155-156, 109 Cal.Rptr.2d 31, 26 P.3d 357.)⁴