People who were not buckled up often assume they have no case. That assumption is wrong in California, and in the auto accident cases we handle it is worth correcting early, before evidence about the belt and the car is lost. California treats a missing seat belt as a possible share of fault, not as a reason to throw out the claim, and the driver who caused the crash still answers for causing it.
This guide explains the seat belt law, how the "seat belt defense" works in a civil case, what the other side has to prove, and how a reduction is calculated if one applies.
How does the seat belt issue play out, step by step?
- Fault for the crash is decided first. The driver who ran the light, followed too closely or turned in front of you is responsible for causing the collision.
- The other side raises the seat belt defense. It claims you were negligent because you were not wearing a belt (CACI 712).
- It must prove four things. That a working belt was available, that a reasonably careful person in your situation would have used it, that you did not wear it, and that your injuries would have been avoided or less severe if you had (CACI 712).
- The last point usually needs expert evidence. The Judicial Council's notes to CACI 712 quote court decisions saying that expert testimony is required to show what injuries you would have had with a belt on.
- The jury assigns percentages of responsibility. If the defense is proven, your damages are reduced by your percentage, and the judge calculates the reduction (CACI 405).
- The rest of the claim stands. Injuries the belt would not have prevented are not reduced on that ground, because the defense has not proven the fourth element for them.
What does California's seat belt law say?
| Rule | What it says | Vehicle Code 27315 |
|---|---|---|
| Drivers | May not operate a vehicle on a highway unless the driver and all passengers 16 or older are properly restrained by a safety belt | Subdivision (d)(1) |
| Passengers 16 and older | May not ride in a vehicle on a highway unless properly restrained by a safety belt | Subdivision (e) |
| Medical exception | Does not apply to a person with a physically disabling or medical condition, certified by a physician or chiropractor, that prevents appropriate restraint | Subdivision (g) |
| Fines | An infraction: no more than $20 for a first offense and $50 for each later one, plus assessments | Subdivision (h) |
| Civil cases | A violation does not establish negligence as a matter of law or negligence per se for comparative fault, but negligence may be proven as a fact without regard to the violation | Subdivision (i) |
Section 27315 was amended effective January 1, 2026, and a replacement version becomes operative January 1, 2027 (Assembly Bill 435 of 2025). The provisions in the table appear in both versions.
Does a seat belt ticket decide the civil case?
No. Subdivision (i) of section 27315 is unusual: it says that breaking the seat belt law does not, by itself, establish negligence in a civil case. The other side must prove negligence as a fact. That is why the jury instruction asks whether a reasonably careful person in your situation would have used the belt, rather than simply whether you broke the law, though the jury may consider the statute in deciding that question (CACI 712).
In practice this means the seat belt issue is decided on evidence: the belt's condition, where you were sitting, how the crash happened and what a qualified expert says about the injuries. A ticket or a line in the police report is not the end of the analysis. Our guide on how to get the crash report in Sonoma County explains how to see what the officer wrote.
How is a seat belt reduction calculated?
California uses comparative fault. If the defense proves its points, the jury decides what percentage of responsibility for your harm belongs to you, and your damages are reduced by that percentage (CACI 405). The percentages for everyone whose fault contributed must total 100 percent (CACI 406).
The reduction applies to the harm the belt would have affected. If a belt would have made no difference to a particular injury, the defense has not proven the fourth element as to that injury. With several defendants, each pays only its own percentage of the noneconomic damages (Civil Code 1431.2); our guide on who pays when several drivers share the fault explains that split.
What changes the answer?
The injured person was under 16. The Judicial Council notes that the seat belt law applies only to persons 16 or older and that no case law has been found on whether younger people can be found comparatively negligent for not wearing a belt (CACI 712, Directions for Use). See how an injury claim works for a child.
No working belt was available. A broken or missing belt defeats the first element of the defense (CACI 712).
A medical condition prevented using a belt. Section 27315 does not apply to a person whose certified condition prevents appropriate restraint (Vehicle Code 27315(g)).
The belt would not have changed the injury. Without proof that injuries would have been avoided or less severe, the defense fails on the fourth element. A serious head injury, for example, needs careful medical analysis; see how a brain injury is proven and valued.
You were also partly at fault for the crash itself. Any share of fault for the collision is a separate question from the belt. Our guide on whether a rear-end collision is always the other driver's fault shows how fault for the crash is weighed.
You were driving uninsured or under the influence. Those raise a different bar on pain and suffering under Civil Code 3333.4, separate from the belt; see pain and suffering when you had no insurance.
What could this look like? An example
For example, imagine a passenger in the back seat who was not buckled when the car she was in was T-boned at an intersection in Rohnert Park by a driver who ran a red light. She suffered a broken femur where the door caved in, and a facial injury from hitting the front seat.
The driver who ran the light is responsible for the collision. His insurer raises the seat belt defense. A working belt was available and she was over 16, so the dispute turns on the fourth element. An expert might say a belt would not have prevented the femur fracture from the intruding door, but would likely have prevented the facial injury. If the jury agreed and assigned her 10 percent of the responsibility for the facial injury, that part of her damages would be reduced by 10 percent, while the femur claim would not be reduced for the belt. This example is made up to show how the rules fit together; it says nothing about any real case.
What mistakes do people make about seat belts and claims?
- Not bringing a claim at all because they were unbuckled.
- Guessing or shading the truth about the belt, which damages credibility on everything else.
- Letting the car be scrapped before anyone checks whether the belt worked.
- Assuming a seat belt ticket decides the civil case, when subdivision (i) says it does not.
- Waiting to see a doctor, which makes it harder to show which injuries the belt would and would not have affected.
What should I do this week?
- Tell your lawyer the truth about the belt, including where you were sitting.
- Ask that the vehicle be kept, or at least photographed inside, including the belts.
- Get medical care and describe every injury, including how it happened inside the car.
- Request the crash report and note what it says about restraints.
- Keep any ticket and the court's paperwork, and note how it was resolved.
- Read our guide on how pain and suffering is valued, since any reduction applies to the damages as a whole.
Frequently asked questions
Will the jury hear that I was not wearing a seat belt?
If the defense has evidence for it, yes. The jury may consider the seat belt statute in deciding whether a reasonably careful person would have worn a belt, and decides what weight to give it (CACI 712).
Who has to prove the belt would have helped?
The defense. Under CACI 712, it must prove that your injuries would have been avoided or less severe with a belt, and the notes to the instruction quote decisions requiring expert testimony on that point.
Does the seat belt defense apply to motorcycle riders?
Motorcycles do not have seat belts, so the defense in CACI 712 does not fit. Helmet rules are different; see e-bike, age and helmet rules for riders of other two-wheeled vehicles.
Can I still recover my medical bills?
Yes. Any reduction is a percentage applied to the damages the jury finds, and only if the defense proves all four elements.
Is not wearing a seat belt a crime?
It is an infraction, not a crime: a fine of no more than $20 for a first offense and $50 for each later one, plus penalty assessments (Vehicle Code 27315(h)). The ticket is separate from the injury claim.
What if a family member who was not belted died in the crash?
The family's wrongful death claim can still go forward. The jury instructions allow the decedent's own share of fault to be weighed (CACI 407), using the same rules described above; see wrongful death when the person was partly at fault.
What if the driver of my car was at fault, not the other driver?
The same rules apply to a passenger's claim against the driver of the car she was riding in.
If you were hurt in a crash and were not wearing a seat belt, you may still have a claim. Contact Young Law Group today at (707) 343-0556 or through our contact page for a free consultation.
Sources
- Vehicle Code section 27315 (safety belts; current version and the version operative January 1, 2027)
- Judicial Council of California: Civil Jury Instructions (CACI), 2026 edition: instructions 405, 406, 407 and 712
- Civil Code section 1431.2 (each defendant's share of noneconomic damages)
- Civil Code section 3333.4 (uninsured and DUI drivers)
