Opinion Evidence in Los Angeles Criminal Courts

When most people imagine a criminal trial, they picture dramatic scientific demonstrations, DNA profiles, ballistics, or fingerprints projected on a screen. Yet a surprising amount of testimony that shapes a jury’s verdict is not scientific at all; it is someone’s opinion. Whether that opinion comes from an eyewitness describing a person’s behavior or from a forensic specialist interpreting lab results, the rules that govern opinion evidence often create key obstacles to admitting evidence in Los Angeles courts and can tip the balance between conviction and acquittal.

This page from Kraut Law Group Criminal & DUI Lawyers explains how opinion evidence works in California criminal cases, identifies the pitfalls that can undermine a fair trial, and outlines proven defense strategies for keeping unreliable opinions out of the courtroom during the Los Angeles criminal process.

An opinion is any conclusion, inference, or impression a witness offers that goes beyond a bare statement of observed facts. California divides opinion testimony into two broad groups:

• Lay opinions: statements by non-expert witnesses based on their perceptions.
• Expert opinions: conclusions offered by witnesses with specialized training, education, or experience.

Both types are admissible only if they meet strict statutory requirements designed to protect juries from speculation, guesswork, and disguised hearsay. A juror may find an opinion persuasive, but only if the judge allows that opinion through the Evidence Code gatekeeping process, overcoming the obstacles to admitting evidence in Los Angeles courts.

The California Evidence Code permits lay opinion testimony when three core conditions are satisfied:

• Direct perception. The witness must have personally seen, heard, or otherwise sensed the matter described.
• Rational connection. The opinion must be logically based on those perceptions rather than on conjecture or second-hand information.
• Helpfulness. The testimony must assist the jury in understanding the witness’s observations or in determining a fact in dispute.

Lay opinion testimony is common because specific experiences are difficult to convey without summarizing impressions. For example, instead of listing dozens of tiny facial details, a witness might simply testify that the driver looked “drowsy” or “intoxicated.” Courts allow that shortcut so long as the underlying observations, such as bloodshot eyes, slow responses, and the odor of alcohol, are potentially subject to cross-examination.

Expert opinions must satisfy additional safeguards because jurors may defer to an expert’s credentials without thoroughly questioning the foundation of the testimony. Under California law, an expert’s opinion:

• Must relate to a subject that is sufficiently beyond common experience so that it would help the trier of fact.
• Must be based on reliable matter, whether or not the matter is admissible, if it is the sort of information experts reasonably rely upon in their field.
• Must not stray into purely legal conclusions reserved for the judge or jury.

In modern Los Angeles courtrooms, experts may testify on a wide range of topics, from cell-site location data to the statistical significance of DNA mixtures. Defense counsel must therefore be ready to examine the expert’s methodology, potential error rates, and any deviations from accepted professional standards.

Some opinion topics appear so frequently in criminal trials that judges and lawyers refer to them as “classic lay opinions. Common examples include:

• Identification of a person or voice. Witnesses often compare an accused’s appearance at trial to what they observed during the incident. Because perception and memory vary, cross-examination focuses on factors such as lighting, duration, stress, and the suggestiveness of any police procedures.
• Apparent intoxication. Jurors routinely hear lay testimony describing slurred speech, impaired balance, and the smell of alcohol as shorthand for being “drunk” or “high.”
• Speed, distance, and time. Drivers, passengers, or bystanders may estimate how fast a vehicle traveled or how long an event lasted.
• Value of property. The owner of an item can give an opinion about its worth, which is crucial in theft and embezzlement cases.
• Emotional state. Witnesses sometimes comment that a person seemed “angry,” “afraid,” or “confused.”

Because these opinions can appear deceptively concrete, an experienced defense attorney probes the witness’s vantage point, viewing conditions, and any prior conversations that could have colored the testimony, creating potential obstacles to admitting evidence in courts.

Practical criminal defense work often hinges on persuading the court to exclude unreliable opinions. Grounds for exclusion include:

• Lack of personal knowledge. If the witness did not directly perceive the event, any opinion rests on hearsay.
• Speculation or conjecture. Opinions that leap beyond observable facts or rely on “gut feelings” risk exclusion.
• Undue prejudice. Even a relevant opinion will be barred if it inflames the jury or invites improper character judgments.
• Improper expert foundation. An expert who relies on untested methods, insufficient data, or novel theories may be disqualified.
• Ultimate legal issue. Witnesses, expert or lay, cannot testify that a defendant is “guilty,” “liable,” or acted “with intent”; those determinations belong to the jury.

At Kraut Law Group Criminal & DUI Lawyers, we scrutinize every opinion offered against our clients. Proven defense tactics include:

• Pretrial motions to suppress. By filing targeted motions, we compel the prosecution to disclose the factual basis, methodology, and qualifications behind each opinion before trial, providing the judge with an early opportunity to exclude weak testimony.
• Comprehensive cross-examination. For lay witnesses, we highlight inconsistencies, sensory limitations, and external influences that may have distorted their impressions. For experts, we scrutinize academic credentials, financial incentives, and deviations from established protocols.
• Competing expert analysis. When scientific or technical opinions are central to the case, we retain independent specialists who can replicate testing, audit laboratory records, and present alternative interpretations.
• Demonstrative aids. Charts, simulations, and photographs can illustrate how an eyewitness’s vantage point or lighting conditions undermine a claimed identification or perception.
• Fact-based narrative. We reinforce the presumption of innocence by anchoring the defense in objective evidence, such as surveillance footage, data logs, and medical records, that provides jurors with a concrete reference point beyond subjective opinions.

While excluding unreliable opinions is essential, mounting a successful defense also means presenting affirmative proof that challenges the prosecution’s narrative. Depending on the charges, counter-evidence may involve:

• Digital tracing. Phone metadata, GPS coordinates, and social-media timestamps that place the defendant elsewhere.
• Medical evaluations. Blood tests or field-sobriety-test re-analysis that contradict lay drunken-driving opinions.
• Financial records. Transaction histories that dispute alleged property values in cases involving theft or fraud.
• Forensic reconstruction. Accident-scene experts who use physics, vehicle dynamics, and environmental factors to contest speed or distance estimates.

A balanced presentation reassures jurors that the defense is not merely poking holes but offering a coherent, fact-supported alternative.

Managing attorney Michael E. Kraut is a former Deputy District Attorney with more than 14 years of prosecutorial insight. That background gives our firm a unique advantage:

• Insider understanding of police investigative techniques. We know how officers train witnesses to make identifications and how lab analysts process evidence, allowing us to expose shortcuts and confirmation bias.
• Credibility with judges and juries. Decades of courtroom experience enable us to translate complex technical debates into plain language that resonates with jurors.
• Resource network. We maintain relationships with preeminent forensic scientists, accident reconstructionists, and psychological experts ready to testify on behalf of our clients.
• Relentless trial preparation. From mock cross-examinations to juror-focused sessions, we test every line of opinion evidence so surprises do not derail a client’s defense.

Our mission is to ensure that only reliable, thoroughly vetted opinions reach the jury and that the jury hears the persuasive factual story that supports your innocence.

If you or a loved one faces criminal accusations in Los Angeles, do not let unchallenged opinion evidence dictate your future. Prompt legal counsel can mean the difference between a conviction built on speculation and a dismissal grounded in fact.

Contact Kraut Law Group Criminal & DUI Lawyers for a comprehensive case evaluation. We are available around the clock to explain your options, preserve critical evidence, and develop a tailored strategy that neutralizes unreliable opinions.