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Updated 2026 by Jared J. Pehrson, Impact Legal Car Accident Attorneys
Most people ask “who’s at fault” like it’s a yes-or-no question. In Arizona, it isn’t. Fault is a percentage. A jury (or an adjuster, before you ever get to a jury) assigns a number to every party involved, and that number decides how much you actually recover. This article walks through how fault is proven in a Phoenix car accident case, what evidence moves the number in your favor, and how insurance adjusters try to move it the other direction.
If you’ve been hit in Phoenix and someone is telling you the crash was partly your fault, understanding this process is the difference between a fair settlement and one that leaves money on the table.
Fault in a car accident case is really a shorthand for negligence, and negligence has the four elements of negligence that have to line up:
Miss any one of those and you don’t have a case. That’s the framework. Everything else on this page is about the evidence that fills in those elements and about the percentage a jury will attach to each driver at the end.
Criminal cases require proof “beyond a reasonable doubt.” A car accident case is civil, and the standard is much lower: preponderance of the evidence. That means “more likely than not.” If the evidence tips the scale even slightly (51% to 49%) in your favor on a given element, you meet the burden on that element.
Practically, this matters in two ways:
The jury (or, in settlement talks, the adjuster) weighs the evidence on each element and on each party’s share of fault. Better evidence wins. That’s why the evidence hierarchy below matters as much as the law does.
Not all evidence is equal. In our experience, the pieces that actually move an adjuster (or a jury) are, in rough order:
Notice where the police report sits. Not first.
Phoenix PD or DPS at the scene will file a crash report and sometimes assign a violation code to one driver. That report is useful. It’s a snapshot of what the responding officer saw and heard in the first 30 minutes after the crash.
But it isn’t the final word on fault. Insurance companies and juries are not bound by it. Officers weren’t at the crash, they’re taking statements from shaken people, and they routinely miss context (a witness who left before they arrived, a traffic camera they didn’t check, an EDR download that hadn’t happened yet). We’ve seen reports blame the wrong driver and we’ve seen reports blame nobody at all.
If you don’t have your report yet, here’s how to get your Phoenix crash report.
The right way to use a police report: as one data point. If it helps you, great. If it hurts you, it can be overcome with better evidence.
Physical evidence doesn’t have an agenda. That’s why it wins fault fights.
Scene photos. Take them if you can (safely). Every angle. Skid marks. Debris field. Traffic signals. Both vehicles from all four sides. Street signs, lane markings, obstructions. Time-stamped.
Vehicle damage patterns. The location and depth of the crumple tells a reconstruction expert the direction of force, roughly how fast each vehicle was going, and which vehicle was moving when the impact happened. A T-bone at the driver’s door tells a different story than a rear corner hit.
Event Data Recorder (EDR) data. Most cars built after 2013 record about 5 seconds of pre-crash data: speed, throttle position, brake application, steering angle, seatbelt status. If liability is disputed, we pull that data. If a commercial truck is involved, the Electronic Logging Device records speed, braking, and hours of service under federal regulations (49 CFR § 395.8). That data can be overwritten or deleted. Getting a preservation letter in the trucking company’s hands within days, not weeks, is critical.
This is the piece of the evidence puzzle that has changed the most in the last two or three years, and it’s usually the piece the other driver doesn’t expect us to go after.
Cell phone records. Subpoenaed carrier records show call and text activity down to the second. In a distracted-driving case, we line that timeline up against the crash timestamp. A text sent at 3:14:52 and a crash at 3:14:58 tells a jury exactly what happened.
In-car telematics from insurers. Progressive Snapshot, State Farm Drive Safe & Save, Allstate Drivewise, Root, and most other carrier apps record speed, hard braking, acceleration, and time of day. If the at-fault driver is enrolled in one of these programs (and millions of Arizona drivers are), that data exists on the insurer’s server. It gets requested in discovery. It sometimes tells a very different story than the driver told the officer at the scene.
Vehicle-manufacturer connected-car data. Later-model vehicles from most major manufacturers transmit driving data back to the OEM. In a serious case, we go after that data too.
Apple and Google location data. Both companies retain granular location history when users have location services enabled. In a hit-and-run or a disputed-position case, that data can place a driver at a specific intersection at a specific second.
Most of this data has retention windows measured in weeks to months. If the case has any signal that distraction, phone use, or speed will be disputed, preservation letters need to go out immediately.
Independent witnesses (people who don’t know either driver) are gold, and their memories fade fast. Within 72 hours, details start slipping. Within a month, an honest person can’t tell you which car had the green light.
What we do early in a case:
Adjusters know witness memory decays. Some of them slow-walk investigations for exactly that reason. Don’t let them.
This is where Phoenix cases get interesting, because most drivers don’t realize how much video exists.
The pattern to notice: almost all of this evidence disappears on a clock measured in days or weeks. This is the number-one reason to get a lawyer involved fast, well before Arizona’s 2-year personal injury deadline becomes an issue.
Reconstruction experts cost money, so they aren’t used in every case. They earn their fee when:
A good reconstructionist can back-calculate impact speed from crush depth, tire mark length, and final rest position. They can also demonstrate sight-lines, reaction times, and what each driver could reasonably have seen and done. In a disputed-fault case, expert reconstruction can meaningfully shift a jury’s fault allocation, and that shift is often measured in real recovery dollars.
The following driver is typically presumed at fault under Arizona’s comparative negligence framework. The reasoning is simple: every driver has a duty to keep enough distance to stop safely, and if they hit the car in front of them, they usually didn’t.
But it’s a presumption, not a rule. Two exceptions come up regularly:
Unjustified sudden stop. When the lead driver brake-checks, stops to yell at another driver, or stops in a live traffic lane for no reason, comparative fault may be assigned to the lead driver.
Non-functioning brake lights. Under A.R.S. § 28-939, motor vehicles are required to have functioning stop lamps. A lead vehicle without working brake lights may bear partial fault for a rear-end collision, because the following driver had no warning that the lead vehicle was slowing or stopped.
We’ve had cases where the rear driver ended up with the majority of fault and cases where the lead driver picked up a significant share. The evidence decides it, not the label “rear-end.”
The vehicle making the left turn is typically at fault when colliding with an oncoming motorcycle. A.R.S. § 28-772 requires a driver turning left to yield to oncoming traffic that’s close enough to constitute a hazard. Because motorcycles are narrower and drivers routinely misjudge motorcycle speed and distance, this is a common serious motorcycle crash patterns in Phoenix. Fault usually lands on the left-turning driver, though speed of the motorcycle can shift a comparative share if the rider was significantly over the limit.
T-bone crashes (also called side-impact or broadside) are almost always intersection crashes, and they turn on one question: who had the right of way? Fault comes down to which driver failed to yield or ran the control.
The evidence that decides it:
A defense you’ll see: “the plaintiff had a stale green” or “the plaintiff entered on yellow.” Signal-phase data usually kills that argument fast, but only if it gets preserved before the city cycles the log.
Truck cases are their own animal. Federal regulations require Electronic Logging Devices to record speed, braking events, and hours of service (49 CFR § 395.8). That data plus the driver’s qualification file, maintenance records, and dispatch records tells you whether the driver was fatigued, speeding, or driving a truck the company knew was unsafe. The preservation letter has to go out fast; some carriers only retain ELD data for the minimum required period.
Here’s the part most drivers, and most competitor websites, gloss over.
Arizona reduces damages in proportion to the claimant’s percentage of fault under Arizona’s comparative negligence rule, codified at A.R.S. § 12-2505.
The formula is:
Total damages × (100% minus your fault percentage) = your recovery
A worked example:
Under A.R.S. § 12-2505(A), even a plaintiff who is 99% at fault can still recover 1% of damages. There is no threshold where partial fault wipes out your case entirely. You don’t need to be blameless. You need to prove the other driver’s share.
That’s why the fault-percentage fight is the fight. Every percentage point the adjuster manages to assign to you comes directly off your recovery.
When there’s more than one at-fault party, Arizona applies several liability, not joint liability. Under A.R.S. § 12-2506, each defendant pays only their assigned fault share. There is no joint payment obligation.
Practical example: three drivers are involved in a chain-reaction crash. The jury assigns 60% to Driver A, 30% to Driver B, and 10% to you. Your damages are $100,000. Your total recovery works out to $90,000, but Driver A owes $54,000 and Driver B owes $27,000 (each pays their assigned share of the reduced total). If Driver B is uninsured and broke, you don’t get to collect Driver B’s share from Driver A. You collect what each defendant owes based on their share.
This is where the “empty chair” issue comes in. A jury can assign fault to a non-party, someone who isn’t in the lawsuit. Maybe it’s a phantom driver who fled the scene. Maybe it’s a party the plaintiff chose not to sue. Defense attorneys often point at the empty chair and blame someone who can’t defend themselves, because every fault percentage assigned to the empty chair reduces what their client owes.
Handling several liability and the empty chair correctly, deciding who to name as a defendant, when to name them, and how to counter empty-chair blame-shifting, is one of the reasons trial-experienced representation matters in cases with more than one at-fault driver.
The comparative fault percentage is the single biggest lever an adjuster has to reduce a settlement. If damages are $100,000 and they can push your fault from 0% to 30%, they’ve cut $30,000 off their exposure. That’s their job.
Common tactics we see:
This is the 2026 version of the same tactic, and it’s aggressive. Defense investigators and adjusters now routinely pull:
We’ve seen adjusters argue plaintiff fault based on a TikTok made months before the crash, and we’ve seen post-crash gym check-ins used to gut a pain-and-suffering claim. That’s why we tell clients to stop posting from the moment the case opens. Lock down privacy settings. Don’t accept new friend requests. Assume everything you post is going to end up on a defense exhibit list.
Independent evidence. Video that shows the light was green. EDR data that shows your speed. Cell phone records that put the phone in their hand, not yours. Reconstruction that shows the crash was physically unavoidable from your position.
The adjuster inflates plaintiff fault; you counter with evidence. That’s the fight.
This 72-hour window is a small piece of the personal injury case process, but it’s the piece that determines everything downstream.
Under A.R.S. § 12-542, you have two years from the date of the injury to file a personal injury lawsuit in Arizona. That deadline gets a lot of attention, and it should. Missing it usually ends your case.
A few important wrinkles:
Here’s what people don’t realize: fault evidence disappears long before month 24. Video is gone in weeks. Skid marks wash away in the next rain. Witnesses move. Memories fade. EDR data on a totaled vehicle disappears when the vehicle is crushed. Telematics and cell records get purged on their own schedules. By the time someone waits 18 months to call a lawyer, half the tools we’d use to prove fault are gone.
The 2-year deadline is the outer boundary. The real deadline for preserving fault evidence is measured in days.
No. The police report is evidence, and often important evidence, but neither the insurance company nor a jury is required to accept it as the final word. We regularly overcome police reports with independent video, EDR data, and witness statements. If your report blames you, that isn’t the end of the case; it’s the start of the fault investigation.
Yes. Arizona applies comparative negligence, and there’s no cutoff where your fault wipes out your case. Even at 99% fault you can technically recover 1% of your damages. Someone 20% at fault with $50,000 in damages recovers $40,000. The insurance company will try to push your percentage up. Independent evidence is what pushes it back down.
The outer deadline to file a lawsuit is 2 years from the date of injury under A.R.S. § 12-542 (or from the 18th birthday for minors under A.R.S. §
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