What is the legal test for admitting expert opinion testimony in a murder trial?

"Evidence Code section 720 provides that a person may testify as an expert 'if he has special knowledge, skill, experience, training, or education sufficient to qualify him,' (id., subd. (a)) which 'may be shown by any otherwise admissible evidence, including his own testimony.' (Id., subd. (b).) The trial court's determination of whether a witness qualifies as an expert is a matter of discretion and will not be disturbed absent a showing of manifest abuse. [Citation.] ' "Where a witness has disclosed sufficient knowledge of the subject to entitle his opinion to go to the jury, the question of the degree of his knowledge goes more to the weight of the evidence than its admissibility." ' " (People v. Bolin (1998) 18 Cal.4th 297, 321-322.) "[A]n expert's qualifications 'must be related to

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the particular subject upon which he is giving expert testimony. Qualifications on related subject matter are insufficient.' " (People v. Chavez (1985) 39 Cal.3d 823, 828.)

"[A]lthough ordinarily courts should not admit expert opinion testimony on topics so common that persons of ' "ordinary education could reach a conclusion as intelligently as the witness" ' [citation], experts may testify even when jurors are not 'wholly ignorant' about the subject of the testimony. [Citation.] '[I]f that [total ignorance] were the test, little expert opinion testimony would ever be heard.' [Citation.] [] Rather, the pertinent question is whether, even if jurors have some knowledge of the subject matter, expert opinion testimony would assist the jury. (Evid. Code, 801, subd. (a), [citation].)" (People v. Prince, supra, 40 Cal.4th at p. 1222.) The Prince court upheld the admission of expert testimony that the unusual manner of stabbing in six murders indicated they were committed by the same person. "Notwithstanding the ability of jurors to review the evidence before them and draw commonsense inferences, it may aid them to learn from a person with extensive training in crime scene analysis, who has examined not only the evidence in the particular case but has in mind his or her experience in analyzing hundreds of other cases, whether certain features that appear in all the charged crimes are comparatively rare, and therefore suggest in the expert's opinion that the crimes were committed by the same person." (Id. at p. 1223.)