Explaining the California Supreme Court’s relatively recent decisions dealing with the admissibility of expert testimony based on hearsay sources, this opinion explains that expert opinion is properly admissible if based on hearsay about background facts or principles of science and the like. (See People v. Sanchez (2016) 63 Cal.4th 665; People v. Veamatahau (2020) 9 Cal.5th 16; People v. Valencia (2021) 11 Cal.5th 818.) However, expert testimony is inadmissible to the extent based on case-specific hearsay. So, in this case involved mesothelioma allegedly caused by asbestos in J&J’s talcum powder products that plaintiff used for decades, plaintiff’s expert’s declarations were inadmissible to the extent they relied on a non-witness’ reports of his findings of asbestos in J&J’s powder. However, the expert’s declaration was admissible to the extent that the expert relied on background, general facts about asbestos, on published reports about asbestos in talc from the mines J&J used to source its powder and other general principles. There was enough of this general background hearsay to support the expert’s inference that J&J’s powder contained asbestos and that it caused mesothelioma in plaintiff, who used the powder for decades and was not otherwise exposed to asbestos. Hence, the trial court erred in granting J&J summary judgment.