What is the legal test for an expert witness?

Generally, a witness may testify only about matters of which he or she has personal knowledge. (Evid. Code, 702, subd. (a).) A lay witness may provide opinion testimony if such opinion is rationally based on the perception of the witness, and is helpful to a clear understanding of his or her testimony. (Evid. Code, 800.) An expert witness, on the other hand, is one who has special knowledge, skill, experience, training, or education sufficient to qualify as an expert on the subject to which his or her testimony relates. (Evid. Code, 720.) An expert may offer opinion testimony if the subject is sufficiently beyond common experience that it would assist the trier of fact. (Evid. Code, 801.) Whether a witness qualifies as an expert is a matter of discretion for the trial court and its determination will not be disturbed unless a manifest abuse of discretion is shown. (People v. Bloyd (1987) 43 Cal.3d 333, 357.)