The other driver says they were not speeding. They say you came out of nowhere. They say there was nothing they could have done.
You know what you saw. The problem is, knowing something and proving it are two very different things in a California injury claim.
Here is what most people do not realize until it is too late: their car may have already recorded exactly what happened. Speed, braking, throttle, seatbelt status, all of it, captured in the seconds before impact. That data exists right now. But it will not exist forever, and the window to preserve it is shorter than most people think.
If you were hurt in a crash and fault is being questioned, this is one of the first things your attorney should be focused on.
What a black box records and what it does not
Most people picture a black box as something that belongs on an airplane. But your car almost certainly has one too.
It is called an Event Data Recorder, or EDR. It is a small module, usually embedded in the airbag control unit, that continuously records a short snapshot of vehicle data. When a crash occurs, that snapshot gets locked in place.
Since 2014, federal regulations have required EDRs in all new passenger vehicles sold in the United States. If your car was built after 2013, there is a very good chance it has one.
What the EDR typically captures in the moments before and during a collision:
Vehicle speed
Throttle position (whether the driver was accelerating)
Brake application and timing
Steering input
Seatbelt status for front occupants
Airbag deployment data
Engine RPM
That is a meaningful picture of driver behavior. If the other driver was doing 65 in a 35, not braking at all, and had their seatbelt off, the EDR may show all of that.
What the EDR does not capture is equally important to understand. It is not a dashcam. It does not record video, audio, or GPS location. It does not tell you where the car was, only what it was doing. For the full picture of a crash, EDR data is one piece of a larger investigation, not a standalone answer.
Why you must act fast
EDR data is not permanent. In most vehicles, the recorder stores only a limited window of pre-crash data, and that data can be overwritten if the vehicle is involved in another collision. More commonly, it can be lost or altered during repairs; once a shop replaces the airbag module or resets the vehicle’s systems, the data may be gone.
Days and weeks matter here, not months. The longer a damaged vehicle sits at a repair shop or insurance lot without a preservation hold in place, the greater the risk that the data disappears before anyone pulls it.
Insurance companies and defense attorneys understand this. In some cases, they move quickly to inspect the vehicle, which can include downloading that data themselves, before you or your attorney have had a chance to act.
The legal tool that protects you is called a spoliation letter, a formal written notice sent to the other party, their insurer, and any relevant repair facility that demands all evidence, including the vehicle and its EDR data, be preserved. Once that letter is sent, destroying or failing to preserve the evidence can have serious legal consequences for the other side.
In California, the EDR data belongs to the vehicle owner, not the insurance company. But ownership does not automatically protect the data. Insurers and opposing parties can subpoena it. The question is whether the data still exists when they do.
That is why the window matters. Getting an attorney involved early, even in the first day or two after a serious crash, is often the difference between having this evidence and losing it entirely.
How EDR evidence is used in a California injury claim
Once the data is preserved and downloaded by a qualified accident reconstructionist, it becomes a powerful tool for building the factual record of what happened.
In practice, EDR evidence can do several things for a claim.
It can establish the other driver’s speed at the moment of impact, which matters enormously when the other side is claiming they were driving reasonably. It can show whether they braked at all before the collision, or whether the braking record shows a last-second reaction that confirms they were not paying attention. It can document whether a seatbelt was fastened, which affects injury causation arguments.
Combined with the police report, witness statements, and medical records, EDR data helps build a timeline that is grounded in numbers, not just competing accounts.
The EDR records your vehicle’s data too. If your speed, braking, or inputs are part of the picture, that information may be in the record as well. California follows comparative fault rules, which means fault can be shared, and the EDR does not take sides. It records what happened in both vehicles.
This is exactly why having an attorney involved before the data is downloaded is so important. Your lawyer can retain an independent reconstructionist, review the data in context, and frame it as part of a complete argument, rather than letting the insurance company’s expert be the only voice interpreting the numbers.
The crash already happened. The data may still be there.
You cannot go back and change what occurred. But right now, in the hours and days after a serious collision, there is evidence that may still exist, evidence that could show exactly what the other driver did and did not do.
The best thing you can do is not wait for the repair shop to finish the job and find out later that the data is gone. One conversation with a personal injury attorney can trigger the preservation process, put the other side on notice, and make sure that evidence is in your corner when negotiations begin.
At Muhareb Law Group, we help injured people in Rancho Cucamonga, Ontario, Fontana, Upland, and throughout the Inland Empire move quickly on exactly these kinds of steps. If you were hurt in a California car accident and want to understand what evidence may be available in your case, contact Muhareb Law Group for a free consultation. We can walk you through where your case stands and what needs to happen next.
Call (909) 519-5832 or reach out online to talk through your situation.
FAQs
Does my car have a black box?
Most likely, yes. Federal regulations have required Event Data Recorders in all new passenger vehicles since 2014, and many vehicles built before that were equipped with them as well. If your car was manufactured after 2013, there is a strong chance it has an EDR.
How long is EDR data stored after a crash?
There is no single answer, it depends on the vehicle. In many cases, the data is stable until the vehicle is repaired, reset, or involved in another collision. That uncertainty is exactly why acting quickly matters. Waiting weeks to address preservation significantly raises the risk the data is gone before anyone looks for it.
Can the insurance company access my car's black box without my permission?
In California, the EDR data belongs to the vehicle owner. The insurance company cannot simply take it. However, they can subpoena the data through the legal process, and they may attempt to access it during a vehicle inspection. Having an attorney send a preservation letter early helps ensure the data is protected and that any access happens on your terms.
What is a spoliation letter and do I need one?
A spoliation letter is a formal written notice demanding that a party preserve all relevant evidence, including the vehicle and its EDR data, in connection with a potential legal claim. If the recipient destroys or fails to preserve evidence after receiving the letter, there can be serious legal consequences. If fault is in dispute and your vehicle or the other driver’s vehicle has an EDR, this letter is often one of the first steps a good attorney takes.
Can black box data hurt my claim?
It can, if your vehicle’s data shows speed or inputs that are inconsistent with your account of the crash. The EDR does not distinguish between drivers, it records what both vehicles were doing. California’s comparative fault rules mean that even if you bear some responsibility, you may still recover damages, but your percentage of fault affects the outcome. This is one reason it matters to have your own attorney review the data before the insurance company’s experts do.