California Evidence Code 720 governs who may testify as an expert witness in state court: a person qualifies if they have sufficient special knowledge, skill, experience, training, or education on the subject of their testimony, and when the opposing party objects, the party calling the expert must prove those qualifications before any opinion is offered.1California Legislative Information. California Evidence Code 720 – Expert Witnesses The statute is short. Its reach is not.
What the Statute Requires
Section 720 has two subdivisions, and both do work. Subdivision (a) sets the substantive standard: enough specialized background to speak credibly on the specific topic at issue. It also says that when an opposing party objects, the offering party has to demonstrate those qualifications before the expert testifies.1California Legislative Information. California Evidence Code 720 – Expert Witnesses
Subdivision (b) governs how qualifications may be proven: through any otherwise admissible evidence, including the witness’s own testimony about their background.1California Legislative Information. California Evidence Code 720 – Expert Witnesses There is no mandatory checklist of degrees or certifications. A mechanic with thirty years of rebuilding transmissions can qualify to testify about transmission failures without a college degree, provided the court finds that experience sufficient for the specific issue in the case.
Two things follow from the statute’s wording. The standard is topic-specific, not general. And any of the listed grounds is enough on its own: knowledge, skill, experience, training, or education. A witness need not have all five.
The Objection Trigger
The formal requirement to lay a foundation kicks in only when the opposing party objects. Without an objection, a witness can offer expert opinion testimony without going through the qualification process on the record.1California Legislative Information. California Evidence Code 720 – Expert Witnesses
In practice, attorneys almost always object or reserve the right to challenge qualifications. Failing to object can waive the right to later argue on appeal that the expert was unqualified. So while the statute technically permits expert testimony without a formal qualification showing, experienced litigators rarely allow that to happen.
How Qualifications Are Demonstrated
When a qualification challenge occurs, the offering attorney typically walks the witness through their background on the stand. The examination covers professional history, academic degrees, specialized training, certifications, publications, prior testimony experience, and anything else that ties the witness’s expertise to the issue in the case. A forensic accountant might describe a CPA license and years spent investigating corporate fraud. A physician might detail board certification, fellowship training, and the volume of relevant procedures performed.
Section 720(b) does not limit the type of evidence that can establish qualifications. The expert’s own testimony counts, and so do documents such as a curriculum vitae, professional licenses, or records of prior court qualifications.1California Legislative Information. California Evidence Code 720 – Expert Witnesses
What matters is fit between the witness’s background and the specific subject of the proposed testimony. A cardiologist with extensive surgical experience may not automatically qualify to opine on psychiatric diagnoses, even though both fall under “medicine.” The court’s inquiry is whether the qualifications match the opinion being offered, not whether the witness is impressive in the abstract.
Voir Dire of the Expert
The formal process for challenging qualifications is called voir dire. Before the expert gives substantive testimony, the opposing attorney questions the witness about their background, training, and experience. This is the opposing side’s chance to surface weaknesses: gaps in education, lack of hands-on work with the specific issue, reliance on outdated methods, or a history of being excluded in other cases. The judge then decides whether the qualifications clear the bar for the topic at hand.
The Judge Decides
Whether a witness qualifies is entirely the trial judge’s call, and California courts take that gatekeeping role seriously. In Sargon Enterprises, Inc. v. University of Southern California (2012), the California Supreme Court confirmed that trial judges have a duty to screen out speculative or unreliable expert testimony. The court held that a judge can and should exclude expert opinions when there is “too great an analytical gap between the data and the opinion proffered.”2Justia Law. Sargon Enters., Inc. v. Univ. of S. Cal.
Sargon rooted this gatekeeping function in Evidence Code Sections 801 and 802. Under Section 801, expert opinion is admissible only when the topic is sufficiently beyond common experience that an expert would genuinely help the jury, and the opinion must rest on the type of information experts in that field reasonably rely on.3California Legislative Information. California Evidence Code 801 Section 802 adds that the court can require the expert to explain the basis for their opinion before delivering it, giving the judge a preview of whether the reasoning holds up.4California Legislative Information. California Evidence Code 802
The judge is doing more than checking credentials. The court evaluates whether the methodology makes sense and whether the conclusions logically follow from the data. An impressive resume alone will not save testimony built on shaky reasoning.
Appellate Review
If a trial judge qualifies or excludes an expert, the losing side can appeal, but the standard of review is abuse of discretion. Appellate courts give trial judges wide latitude on these calls. Sargon expressly affirmed this deferential standard, meaning an appellate court will overturn a qualification ruling only when the trial judge’s decision was clearly unreasonable, not merely debatable.2Justia Law. Sargon Enters., Inc. v. Univ. of S. Cal. As a practical matter, that makes the trial court’s gatekeeping decision close to final in most cases.
Scope After Qualification
Qualifying under Section 720 does not hand the witness an open microphone. Testimony must stay within the boundaries of the expertise the court recognized. A biomechanical engineer qualified to testify about crash forces cannot pivot mid-testimony to diagnosing the plaintiff’s traumatic brain injury. That is a different specialty with its own foundation.
Section 801 imposes an additional limit. The topic must be sufficiently beyond everyday experience that an expert’s input would actually help the jury.3California Legislative Information. California Evidence Code 801 Courts will exclude expert testimony on matters a reasonable person can evaluate without help. Whether a floor was wet and slippery is something a jury can assess from lay testimony and photographs. Whether a specific floor wax compound reduced friction below safe thresholds is something a materials scientist can address in a way the jury cannot reach on its own.
What Section 720 Does Not Cover
Section 720 answers whether the person is qualified. It does not address two related questions that often come up in the same trial.
The first is whether the underlying scientific technique is trustworthy enough to be admitted at all. California uses the Kelly/Frye standard for that, drawn from People v. Kelly (1976), which requires that a novel scientific technique be “generally accepted” in the relevant scientific community.5Justia Law. People v. Kelly A witness can be perfectly qualified under Section 720 and still see their testimony excluded because the method behind it fails Kelly/Frye.
The second is pretrial disclosure. Code of Civil Procedure Section 2034.260 requires parties to exchange written expert witness lists and sworn declarations describing each expert’s qualifications, expected testimony, availability, and fees before trial.6California Legislative Information. California Code of Civil Procedure CCP 2034.260 Missing that exchange can bar the expert from testifying entirely, before Section 720 ever enters the picture.
And in some cases, no expert is needed. When the alleged conduct is so obvious that anyone could recognize the problem, California courts allow the jury to decide without expert help. A surgeon leaving an instrument inside a patient is the classic example. Diagnostic errors, medication interactions, and judgment calls in treatment almost always require expert testimony because those issues fall outside what a typical juror can evaluate independently.