What Evidence Should Be Preserved After a California Truck Accident?

After a truck accident in California, the evidence that matters most falls into three groups: electronic data from the truck, company records from the motor carrier, and physical evidence from the vehicles and the scene. Preserve the electronic logging device and hours-of-service records, the engine control module download, telematics and dashcam video, dispatch and maintenance records, driver qualification and testing files, both vehicles before repair, and scene photos with witness information. Much of this evidence has a short legal lifespan. Federal rules allow carriers to destroy driver inspection reports after three months and hours-of-service records after six months, and onboard data can be overwritten far sooner. This article is general information, not legal advice.

Truck crash evidence disappears on a schedule

A collision between two passenger cars is usually decided by what happened at the scene. A commercial truck case is different. The most important proof is often in records the trucking company controls, and federal regulations set minimum retention periods for those records. Once a retention period expires, the carrier may legally destroy the material. That is why a preservation letter, sometimes called a spoliation letter, should go out promptly. It identifies the crash and the categories of evidence, and it tells the carrier, the driver, the vehicle owner, the shipper, the broker, and the maintenance provider to suspend routine destruction. A letter cannot guarantee that every device stored the data you need, but without one, evidence routinely vanishes on schedule.

In my practice, the preservation letter goes out within days of being hired, sometimes the same day. The 90-day window on driver inspection reports is the one that catches people off guard. Three months sounds like plenty of time until you realize how much has to happen first.

Electronic evidence from the truck itself

Modern commercial trucks record a detailed account of their own operation. Four sources matter most. The electronic logging device (ELD) records driving time, on-duty time, and rest breaks. Under 49 CFR 395.8(k)(1), a motor carrier must keep records of duty status and supporting documents for at least six months from the date of receipt. Supporting documents are the paper trail that tests the log against reality: fuel receipts, toll transactions, dispatch messages, bills of lading, and delivery timestamps. Together they show where the truck actually was and when, which either backs up the log or exposes gaps in it. The engine control module (ECM), often called the truck’s black box, records pre-crash speed, brake application, throttle position, and fault codes. A qualified expert downloads this data and uses it to reconstruct the seconds before impact. The download must happen before the truck is repaired, sold, or sent to salvage, because once the vehicle is gone, so is the data. Telematics and fleet management systems add GPS breadcrumb trails, speed histories, and hard-braking events. Dash cameras, both forward-facing and driver-facing, can show the moments before impact and the driver’s condition. Video is frequently overwritten within days or weeks, which makes it some of the most time-sensitive evidence in the case.

I have a qualified expert download the ECM data before the truck is repaired or sold. Once that vehicle is gone, the data goes with it, and no court order can bring it back.

Company records that reveal the bigger picture

The truck’s data shows what the vehicle did. The company’s records show why. Dispatch records and bills of lading reveal pickup and delivery windows, which can show whether the driver was under schedule pressure. Maintenance and repair records show the history of brakes, tires, steering, and lighting. Under 49 CFR 396.3(c), carriers must keep maintenance records for one year where the vehicle is housed, plus six months after the vehicle leaves their control. Driver vehicle inspection reports, the daily write-ups in which drivers note defects and companies certify repairs, carry the shortest fuse: 90 days under 49 CFR 396.11. If a driver reported a brake problem and the company did nothing, that report is the document that says so, and it can be lawfully destroyed three months later. The driver qualification file holds the application, employment history, safety performance history obtained from prior employers for the previous three years, road test results, and the medical examiner’s certificate. Carriers must keep it for the duration of employment plus three years under 49 CFR 391.51. Drug and alcohol testing records for positives and refusals must be kept for five years. The accident register must be kept for three years under 49 CFR 390.15.

Physical and scene evidence

Both vehicles should be inspected before repair, sale, or destruction. Crush patterns, brake and tire condition, lighting, and underride damage all tell a story that photographs alone cannot. At the scene, preserve photos and video of vehicle positions, skid marks, debris fields, road surface conditions, signage, sight lines, and lighting. Collect witness names and phone numbers promptly, request 911 audio, and obtain the police traffic collision report.

Evidence checklist: what to preserve after a truck crash

• Electronic logging device data and hours-of-service records, with supporting documents such as fuel receipts, toll records, and dispatch messages.
• Engine control module downloads from every involved commercial vehicle, performed before repair or salvage.
• Telematics and GPS data from the carrier’s fleet management system.
• Dashcam video from all cameras on the truck.
• Dispatch records, bills of lading, and delivery receipts showing the schedule the driver was under.
• Maintenance, inspection, and driver vehicle inspection records.
• Driver qualification, medical certification, and drug and alcohol testing files.
• Both vehicles, unrepaired and unsold until inspected, plus scene photos, witness contacts, 911 recordings, and the police report.

How this evidence connects to a California injury claim

Evidence is only useful if it proves something the law cares about. Speed and braking data support a negligence claim against the driver. Hours-of-service records and supporting documents support a fatigue theory. Maintenance records support negligent maintenance. Qualification and testing files support claims for negligent hiring, supervision, training, or retention against the company. Dispatch and broker records can support claims against others in the transportation chain, because responsibility for a commercial crash is not always limited to the person behind the wheel. California applies comparative fault, which means the defense will argue that the injured person shares responsibility. Complete records keep that argument grounded in facts rather than speculation. An early, methodical preservation effort is what makes that possible. If you or a family member was hurt in a crash with a commercial truck, contact our office promptly for an evidence-preservation plan, before vehicles are repaired and electronic records are overwritten. Consultations are free, and you can learn more about how long your case may take, what your claim may be worth, and see our past case results.

A walkthrough: how the pieces fit together

Consider a nighttime rear-end collision on I-5. The truck’s ECM download shows no braking before impact and a speed above the posted limit. The ELD shows the driver within legal hours, but fuel receipts and toll records place the truck 400 miles away two hours before the crash, which the log cannot explain. The driver vehicle inspection reports from the prior month note a brake adjustment issue, and the maintenance file shows no repair order. The driver qualification file shows a prior employer flagged hours-of-service violations that the carrier never followed up on. No single document proves the case. Together, they support claims for driver negligence, fatigue, negligent maintenance, and negligent hiring and supervision. That is why the checklist above treats electronic data, company records, and physical evidence as one package.

What if the evidence is already gone?

Sometimes the preservation letter arrives too late. The truck has been repaired, the dashcam has overwritten itself, or the carrier destroyed records after the retention period expired. The case is harder, but it is not necessarily over. Police reports, 911 audio, witness statements, scene photographs, and the injured person’s own vehicle data may still establish what happened. When evidence was destroyed after a party knew it should have been kept, California courts can address spoliation in ways that range from evidentiary sanctions to adverse inferences, depending on the facts. These issues are highly fact specific, which is another reason the preservation effort should start immediately rather than after the first round of discovery.

Attorney Q&A: Preserving Truck Crash Evidence

Q: When someone hires you after a truck crash, what is the first thing you do to lock down the evidence?

A: The very first thing we do is send a detailed evidence preservation letter to all the parties we can identify as being involved. All preservation letters should be specifically tailored to the case type, but given that the trucking industry is heavily regulated, the preservation letter really needs to be trucking-industry specific.

Q: What is the piece of evidence you see disappear most often before a lawyer gets involved?

A: Unfortunately, the physical evidence at the scene of the crash is often the most common evidence to disappear, because lawyers are often not retained until days or weeks after the crash. That is not to say that evidence cannot still be present at the scene. The scene should always be inspected for that evidence, but after several days or weeks, evidence on the roadway can disappear.

Q: Who receives your preservation letter, and how fast does it go out?

A: As I mentioned above, the very first thing we do is send out preservation letters. These really go to everybody we can identify as involved, whether that be the driver, carrier, broker, shipper, or any other party involved.

Q: The carrier says the dashcam video was already overwritten. What then?

A: We certainly do not take carriers at their word when it comes to whether or not a dash cam video was overwritten. We would request that the truck be taken out of service until we have had an opportunity to have our own experts examine it.