Trial court’s erroneous admission of non-testifying expert’s testimony violated defendant’s right of confrontation and constituted prejudicial error. Merolillo was convicted of the first degree murder of a carjacking victim who died of an aortic aneurysm a month after the offense. Causation of death was the key trial issue. The pathologist who testified at the preliminary hearing and who opined the death was caused by trauma inflicted during the carjacking, did not testify at trial. Over defense objection, the pathologist’s testimony was elicited via prosecution cross examination of a defense medical expert. The state Court of Appeal found the trial court’s error in allowing the pathologist’s testimony to be introduced during cross examination to be harmless. Review was denied. The Ninth Circuit reversed. Merolillo’s right to confront the pathologist was violated by the admission of the experts preliminary hearing testimony. Applying the non-exclusive factors announced by the Supreme Court in Delaware v. Van Arsdall (1986) 475 U.S. 684, the court held this error had a “substantial and injurious effect or influence in determining the jury’s verdict.” The pathologist’s testimony went to the heart of the causation issue; his testimony was not merely cumulative, as he was the only pathologist who performed the autopsy; his testimony was not corroborated by the other experts; he was not called as a witness; his preliminary hearing testimony “does not in itself satisfy the objectives of the Confrontation Clause under pre-Crawford law;” and the prosecution case turned on the issue of causation, as to which the experts disagreed.