What is the test for a defendant to appeal against the findings of an expert in a medical malpractice case?

^2. To the extent that the reply brief raises issues not headed and argued in the opening brief, we decline to consider them. (See Utz v. Aureguy (1952) 109 Cal.App.2d 803, 808.)

^3. To the extent that defendant argues on appeal that the expert's conclusions were flawed, the time to raise this challenge was in the trial court. (See People v. Weaver (2001) 26 Cal.4th 876, 904 ["To the extent defendant attempts to impugn the validity of the appointed experts' conclusions . . . , the time to raise such a challenge has long since passed. . . . [D]efendant may not now relitigate that question with arguments he did not make below"]; People v. Bolin (1998) 18 Cal.4th 297, 321 [defendant's contention that evidence was inadmissible "because the witness was not qualified to render an expert opinion" was forfeited for lack of objection in the trial court].)