Truck accident cases are fundamentally different from car accident cases — not just in the severity of injuries, but in the way evidence works. When a passenger vehicle collides with an 80,000-pound commercial truck, the physical destruction is obvious. What is less obvious is that some of the most important evidence in the case begins disappearing within hours of the crash, and the trucking company’s legal team may already be working to control what survives.
Commercial trucks are rolling data centers. Modern semi-trucks are equipped with electronic logging devices (ELDs), event data recorders (EDRs), GPS tracking systems, forward-facing cameras, and engine control modules — all of which capture information that can be decisive in a liability case. The problem is that much of this data is stored on systems that overwrite themselves automatically, and trucking companies are not always required to preserve it unless they receive a formal legal demand.
Unlike a car accident where the primary evidence is the vehicles themselves and the police report, a truck accident case can involve federal regulatory violations, corporate negligence, third-party maintenance contractors, and insurance structures that span multiple entities. Each of those layers has its own evidence — and its own timeline for how long that evidence exists.
Every commercial truck manufactured after 2000 is equipped with an Electronic Control Module (ECM), commonly referred to as a black box. This device continuously records data including vehicle speed, engine RPM, brake application, throttle position, and in many cases, whether the driver was wearing a seatbelt at the time of impact.
In the seconds before a crash, this data can definitively answer questions like: Was the truck traveling over the speed limit? Did the driver attempt to brake? Was the engine running normally, or were there mechanical warnings being ignored? This information is extraordinarily powerful in establishing liability.
The critical vulnerability: most ECMs overwrite their data on a rolling basis. Depending on the system and how much the truck has been driven since the accident, that data can be gone within 30 days — and sometimes within 72 hours if the truck returns to service immediately. Trucking companies are under no automatic legal obligation to preserve this data unless they receive a written preservation demand.
Since December 2017, the Federal Motor Carrier Safety Administration (FMCSA) has required most commercial truck drivers to use Electronic Logging Devices (ELDs) to record their hours of service. These devices connect directly to the truck’s engine and automatically record driving time, on-duty time, and rest periods.
Hours of service violations are one of the leading contributors to serious truck accidents. Under FMCSA regulations, most commercial drivers are limited to 11 hours of driving within a 14-hour window, and must take a 10-hour rest break before driving again. A driver who has been behind the wheel for 14 straight hours is statistically as impaired as a driver with a blood alcohol content above the legal limit.
ELD data showing a driver exceeded their legal driving hours is some of the most damaging evidence possible in a truck accident case. FMCSA regulations require carriers to retain these records for six months — but again, that retention period begins from the date of the record, not the date of the accident. A preservation demand must be sent immediately.
Many commercial trucks now carry forward-facing and cab-facing cameras that record continuously, overwriting footage on a loop every 24 to 72 hours. This footage can show exactly what the driver was doing in the moments before impact — whether they were looking at their phone, eating, adjusting the radio, or simply not paying attention to the road ahead.
Beyond the truck’s own cameras, the crash scene itself may be covered by traffic cameras, business surveillance systems, and highway cameras operated by the Arizona Department of Transportation. ADOT’s cameras typically overwrite footage within 72 hours. Business surveillance systems vary widely — some retain footage for 30 days, others for as little as 24 hours. Identifying and requesting this footage must happen fast.
Under FMCSA regulations, trucking companies are required to maintain a qualification file for every driver they employ. These files must include the driver’s application for employment, motor vehicle record, road test certificate, medical examiner’s certificate, and documentation of any prior violations. When a truck driver causes a serious accident, their qualification file can reveal whether the company knew — or should have known — that the driver was unfit to operate a commercial vehicle.
Post-accident drug and alcohol testing is mandatory under federal law when a crash results in a fatality, an injury requiring immediate medical treatment away from the scene, or a vehicle being towed. The results of these tests must be retained for five years if positive, and for one year if negative. If a company fails to conduct mandatory post-accident testing, that failure itself is evidence of negligence.
Commercial trucks are required to undergo regular inspections, and drivers must complete a pre-trip and post-trip inspection report every day. These records can reveal whether a mechanical defect — brake failure, tire problems, steering issues — was known before the crash but not repaired. If a trucking company’s own maintenance records show that a brake problem was flagged three weeks before a fatal accident and never fixed, that is not just negligence — it is the kind of evidence that can support a punitive damages claim.
Vehicle inspection reports must be retained for 12 months under federal regulations. However, if the truck is sent for repairs immediately after the accident — which companies sometimes do — the physical evidence of the defect may be altered or destroyed before it can be independently examined.
A spoliation letter, or evidence preservation letter, is a formal legal notice sent to the trucking company, its insurer, and any third parties (maintenance contractors, freight brokers, etc.) demanding that all potentially relevant evidence be preserved immediately. Once received, the company has a legal obligation to halt any automatic data deletion, pull the truck from service to preserve its physical condition, and retain all records related to the driver, the vehicle, and the trip.
If a company destroys evidence after receiving a preservation letter, courts can impose severe sanctions. In Arizona, a jury can be given an “adverse inference” instruction — meaning they are told they may assume the destroyed evidence would have been harmful to the company’s case. In some situations, courts have granted summary judgment against companies that engaged in deliberate spoliation.
The single most important thing a truck accident victim can do is contact an experienced Arizona truck accident attorney as quickly as possible after the crash. Not next week. Not after you have recovered from your initial injuries. Immediately.
At Phillips Law Group, our truck accident team sends preservation letters within hours of being retained. We work with accident reconstruction specialists, former FMCSA investigators, and trucking industry experts who know exactly what evidence exists, where it is stored, and how to get it before it disappears. Call us at (602) 222-2222 for a free consultation. The clock is already running.
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