How Is Fault Determined in a Car Accident? A Simple Guide

By the Mercury Team

Each year, tens of thousands of Americans get into collisions ranging from fender benders to fatalities. And if you’ve just been in a crash, you might be wondering how fault is determined and what it means for your claim and your insurance premium. Here’s what you need to know about at-fault and not-at-fault accidents, along with factors insurance companies use to determine responsibility.

What Is an At-Fault Accident?

An at-fault accident means you are considered legally responsible for causing the crash, based on the facts of the accident and applicable state laws. It typically involves violating a traffic law or acting negligently, like rear-ending another vehicle or running a red light. In these cases, your insurance usually pays for the other driver’s damages, up to your policy limits.

What Is a Not-at-Fault Accident?

A not-at-fault accident means the other driver caused the crash, and their insurance is generally responsible for covering your damages. Keep in mind that even if you’re not at fault, your insurer may still step in initially—especially in certain states—before seeking reimbursement from the other party’s insurer.

How Do Insurance Companies Determine Fault?

When an accident occurs, your insurance company will investigate multiple sources of evidence and apply state laws to assign responsibility. “Fault is based on evidence, consistency, and how the events align with traffic laws,” says Heather B Paull, Manager, Divisional Claims. “Even small details can shift liability.”

That’s why adjusters review documents, compare statements, and reconstruct what likely happened. Their goal is to determine liability based on facts and not just who filed the claim first.

Key Factors Used to Determine Fault in a Car Accident

Here are a few of the most common types of evidence used to determine whether a driver is at fault or not:

Police Reports and Statements

Officers document the scene, note violations, and may indicate who they believe caused the accident. While their observations aren’t necessarily final, they do carry significant weight in the eyes of an insurance company.

State Traffic Laws

Adjusters also compare each driver’s actions against state and local laws, such as right-of-way rules, speed limits, and signaling requirements.

Witness Accounts and Evidence

Your adjuster may look at third-party witness accounts, and they’ll likely take a statement from both parties in the accident.

Photos, Videos, and Dash Cams

Visual evidence often becomes the deciding factor, especially when stories conflict. Clear images from a nearby business’s camera or a traffic cam of damage, positioning, and road conditions can strongly influence the outcome of who’s at fault.

How Fault Works in At-Fault vs. No-Fault States

Keep in mind that fault rules will vary based on where you live. States like Kansas, Utah, and New York are considered no-fault states, but drivers must carry Personal Injury Protection (PIP) coverage. Thirty-eight states and Washington, D.C. are currently at-fault states, including Alabama, Georgia, Oklahoma, and South Carolina.

• In an at-fault state, the driver’s insurance pays for property damage and physical injury costs, lost wages during any recovery, and vehicle repairs.
• In no-fault states, each driver’s PIP pays for their own lost wages and medical expenses as a result of the accident, regardless of fault.

What Happens If Both Drivers Share Fault?

In many states, fault can be split between drivers. This is called comparative or contributory negligence. “Let’s say you’re found 30% responsible and the other driver is 70% at fault,” explains Heather B Paull, Manager, Divisional Claims. “Your compensation may be reduced by your percentage of fault.” Keep in mind that states handle shared fault differently, and the percentage of fault that affects your claim may not be the same percentage that makes an accident chargeable for insurance rating purposes.

How Fault Impacts Your Insurance Rates

The impact on your insurance rates will depend on where you live and whether you’re at fault:

• Being involved in an at-fault accident typically leads to higher premiums because insurers see you as a higher risk. However, whether an accident is chargeable can vary by state, insurer, and the details of the claim.
• A not-at-fault accident may have little to no impact on your rates, though this can vary by insurer and state.

What to Do After an Accident to Help Prove Fault

While it’s easy to get flustered after someone crashes into your vehicle, taking a few proactive steps can help alleviate insurance headaches later on:

• Call the police and get an official report.
• Take photos of all vehicles, damage, road conditions, and signs.
• Gather contact and insurance information from all drivers.
• Speak with witnesses, and get their contact details.
• Avoid admitting fault at the scene.
• Notify your insurer as soon as possible.

If you’re dealing with a recent crash, understanding how fault is determined in a car accident can make all the difference in how your claim plays out. After a collision, be sure to examine your evidence, understand your state’s rules, and make sure you have clear documentation for your side of the story. If you have questions or want to review your auto insurance coverage, Mercury offers 24/7 support and a 365-day-a-year claims process.

FAQs

Can fault be changed after an initial insurance decision?

Yes. New evidence, like video footage or additional witness statements, can lead insurers to reassess and adjust fault determinations.

Do insurance companies always agree on who is at fault?

Not always. Each insurer conducts its own investigation, and disagreements can lead to negotiations or even legal action.

How long does it take to determine fault after an accident?

It can take anywhere from a few days to several weeks, depending on the complexity of the case and the availability of evidence.