Written and reviewed by Josh Kohanim, Esq., California Bar No. 328609 · Reviewed
In this guide
The rear driver's presumed fault
Fault in a Los Angeles rear-end crash turns on the presumption, its exceptions, the proof, chain collisions, and the argument that starts after liability is admitted. What to do at the scene and in the first few days is in our post on what to do if someone rear ends you.
The rule starts with a duty. Vehicle Code section 21703 says the driver of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of that vehicle and the traffic upon, and the condition of, the roadway. Following distance is the space you keep so you can stop for whatever the car ahead does. Section 22350, the basic speed law, adds that nobody may drive faster than is reasonable or prudent for the weather, the visibility, the traffic, and the road. Civil Code section 1714 makes everyone responsible for an injury caused by a want of ordinary care.
Put those together and the driver who hit you has to explain why he could not stop. Usually he cannot. In Los Angeles, where stop-and-go traffic makes the rear-end the default crash, that explanation is missing in most files we open. The California Office of Traffic Safety recorded 8,116 people killed and injured in fatal and injury collisions in the City of Los Angeles in 2023.
Limits of the rear-end rule
A rebuttable presumption is a starting point the law adopts until evidence displaces it. It is not a verdict. When a statute like section 21703 is violated and the violation causes the harm the statute was written to prevent, a California jury can be instructed on negligence per se, the doctrine that treats the violation itself as negligence. That instruction is CACI 418, and the general duty instruction the same jury reads first is CACI 700, Basic Standard of Care, both published in the 2026 edition of the Judicial Council of California Civil Jury Instructions.
Insurance adjusters apply a rougher version of the same idea. The claim opens with the rear driver at fault, and the file only moves if the rear driver's insurer produces something. In practice, the burden sits on the other side, and their first move is usually to look for one of the five exceptions below. Knowing which one they are reaching for tells you what evidence to preserve this week.
The front driver's share of fault
| Situation | Why the front driver may be at fault | Statute | What proves it |
|---|---|---|---|
| Brake check or a sudden stop with no reason | Stopping or slowing sharply without signaling when there was a chance to signal | Vehicle Code 22109 | Dashcam, event data recorder, a witness, the absence of any hazard ahead |
| Cutting in, then braking | The safe following distance never existed because the front car created the gap | Vehicle Code 22350 and 21703 applied to the merging driver | Damage angle, lane position at impact, a witness, video |
| Brake lights not working | The rear driver got no warning the front car was slowing | Vehicle Code 24603 lighting requirements | Photographs at the scene, the repair order, a post-crash inspection |
| Reversing into the car behind | Backing is governed by a different rule than following distance | Vehicle Code 22106 | Crush direction, bumper height marks, transmission data |
| A third car pushed the rear driver forward | The driver who started the chain caused the impacts ahead of him | Apportionment, CACI 406 | Sequence of impacts, single versus double impact damage, 911 timeline |
The brake check row is the one insurers reach for most, and it has a statute behind it. Vehicle Code section 22109 says no person shall stop or suddenly decrease the speed of a vehicle on a highway without first giving an appropriate signal to the driver of any vehicle immediately to the rear when there is opportunity to give the signal. Stopping for a hazard is not a violation. Stopping without warning when there was time to warn is. That distinction decides the argument, and it is a factual question about what was ahead of you.
The reversing row is a different case. Vehicle Code section 22106 says no person shall start a vehicle stopped, standing, or parked on a highway, nor back a vehicle on a highway, until the movement can be made with reasonable safety. If the front car backed into you, the following-distance analysis never applies at all, and the physical evidence usually settles it quickly.
Evidence that decides the dispute
Six evidence types carry these disputes, and four of them decay within weeks.
- Damage geometry. Where the crush is, how high it sits, and whether one bumper rode over or under the other. A bumper-under-bumper override tells you about relative braking and ride height at impact, and it is why the vehicles should be photographed from every side before anything is repaired.
- The event data recorder. Most modern vehicles store a few seconds of pre-crash data: speed, throttle, brake application, and seat belt status. An event data recorder download from both cars can show whether the front car braked with nothing ahead of it, or whether the rear car never braked at all. The module can be lost when the car is sold or scrapped.
- Video. Dashcams in both cars, doorbell and business cameras along the block, and transit and freeway camera systems. Most of it overwrites itself on a cycle measured in days, so the request has to go out immediately.
- The 911 timeline. Call times and dispatch logs establish the sequence in a chain collision better than anyone's memory does, and they are generated by a neutral system.
- Witnesses, found in week one. A neutral witness located a month later remembers a crash. A neutral witness located in week one remembers whether your brake lights came on.
- Scene evidence. Skid marks, gouge marks, fluid trails, and debris fields fix the point of impact and the direction of travel. Rain and street sweepers erase them.
One caution about the collision report. It is a valuable record of who was present and what the roadway looked like. The officer's opinion about fault, though, was formed in twenty minutes at a curb, usually with no vehicle data and sometimes without hearing from one driver at all. An adjuster who quotes it as final is stating a negotiating position.
Chain collisions in Los Angeles
A chain collision is a crash involving three or more vehicles in a line, and on the 405 at 6 p.m. it is the normal shape of the event. Everyone blames the car behind them, which is why these files stall. The correct analysis is apportionment rather than a two-car rule applied three times: dividing responsibility among everyone whose conduct caused a given impact, the subject of CACI 406.
The question that decides it is how many impacts each vehicle took, and in what order. A car struck once from behind and pushed forward shows a different damage signature than a car that struck the vehicle ahead under its own power and was then struck from behind. Front and rear crush, headrest and seat deformation, and the occupants' accounts of how many jolts they felt all speak to this. So does the 911 log. If you were pushed into the car ahead of you, you are a plaintiff in that collision, not only a defendant.
Disputes over the injury alone
This is the majority of rear-end cases. The other driver's insurer accepts fault in the first two weeks. Nothing about the crash is in dispute. Then the adjuster sends you a photograph of a scuffed bumper and argues that a collision that gentle could not have caused a herniated disc. That is where the case is won or lost.
The argument has a name. A biomechanical defense is an opinion, usually from an engineer, that the forces in a low-speed impact were too small to injure the human body in the way claimed. It is an average applied to a specific person, and two California jury instructions exist precisely because people are not averages.
CACI 3927 addresses aggravation of a preexisting condition: a defendant is responsible for harm caused by making an existing condition worse, even though the condition was already there. CACI 3928 states the unusually susceptible plaintiff rule, often called the eggshell plaintiff rule: a defendant takes the injured person as he finds him, and is not excused because a healthier person might have walked away. A degenerative disc that never hurt before the crash and hurts every day after it is the claim itself.
The answer to the low-impact argument is built in the first month. A medical visit the day of the crash listing every symptom. Continuous treatment with no unexplained gaps. A treating physician who writes causation into the chart rather than leaving it to be inferred. And photographs of more than the dent: the seat, the headrest, the interior, and the position of the cars. Our guide to car accident injuries covers what each injury requires the file to prove.
The cost of partial fault
California uses pure comparative fault: a jury assigns each party a percentage of responsibility and reduces that party's damages by their own share, with no cutoff. CACI 405 covers the plaintiff's comparative fault and CACI 406 covers apportionment among multiple defendants. The arithmetic is plain. On damages found at $200,000, a plaintiff assigned 20 percent of the fault recovers $160,000. At 60 percent, the same plaintiff still recovers $80,000. Nothing in that math ends the claim.
That is why the exceptions above matter less than people assume. An insurer arguing that your brake lights were dim is usually trying to buy a percentage rather than defeat the claim.
Rear-end case value
The number is decided by three things: the strength of the liability evidence, the quality of the medical documentation, and the insurance coverage available. A minor damage photograph is not one of them. One of our own rear-end cases opened with an offer of $31,500 and resolved for $1,250,000 after back surgery.
Rear-end crash, herniated disc
Hit at a stoplight by a texting driver on the job. Back surgery, then a real settlement.
Prior results do not guarantee a similar outcome. Every case depends on its own facts, injuries, and insurance coverage. Amounts shown are gross recoveries before attorney's fees, costs, and medical liens.
We publish the first offer next to the recovery because the gap is normal. The first offer is a negotiating position made before the file is complete, and it is priced off what the adjuster knows in month two. Our guide to what actually caps a settlement explains what moves it and what cannot be moved.
Exceptions to the rear-end rule
- Parking lots and driveways. A backing collision in a lot is governed by Vehicle Code 22106 and by ordinary care, not by following distance. Fault often turns on who was already established in the lane.
- A public agency vehicle. If a Metro bus, a city truck, or a school district van hit you, present a government claim within six months under Government Code section 911.2. That deadline controls everything else.
- Nobody was hurt and the damage is small. Then this is a property damage claim, and it is worth exactly the repair. Photograph it, file the SR-1, the DMV's accident report form, if the damage passed $1,000, and read the release before you sign.
- A commercial truck was involved. The evidence set changes completely, and some of it is destroyed on a schedule. Our Los Angeles truck accident lawyer page covers what has to be preserved and how quickly.
| What ends | Deadline | Source |
|---|---|---|
| Lawsuit for personal injury | 2 years from the crash | Code of Civil Procedure 335.1 |
| Claim against a public entity | 6 months from accrual (usually the crash date) | Government Code 911.2 |
| Written report after an injury crash | 24 hours | Vehicle Code 20008 |
| SR-1 to the DMV | 10 days | Vehicle Code 16000 |
| Uninsured motorist claim: suit, written settlement, or arbitration demand | 2 years from the crash | Insurance Code 11580.2 |
Fault in your crash
Almost certainly the driver behind you, because he had a duty to leave room and did not. If his insurer wants a different answer, it has to produce evidence for one of five narrow exceptions, and the evidence that answers it is decaying now in a body shop and on a security camera. If it does concede fault, expect the argument to move to your neck instead of your bumper, and expect that argument to be made with a photograph.
Tell an attorney what happened and we will tell you what the file needs before it disappears. We send the preservation requests, we handle the recorded statement, and there is no fee unless we recover. Our Los Angeles car accident lawyer page explains how the claim is built, and our guide to filing a car accident claim in Los Angeles puts the deadlines in order.