Author: John Mattiacci | Owner Mattiacci Law
Published January 5, 2026
Figuring out who caused a car accident can feel confusing, especially when you’re standing there staring at two busted bumpers and everyone has a different story.
It’s easy to wonder how the police sort it all out.
Do they go by damage? Do they guess? Do they just pick a side?
Luckily, it’s a lot more organized than it looks.
Police follow a clear process to figure out what actually happened and who made the mistake that led to the crash. They look at the scene, talk to people, check the rules, and use whatever evidence they can find.
In this post, we’ll show you how police officers determine fault after an accident.
#1. Observing The Scene
The first thing officers do is take in the scene.
They look at everything as it is right after the crash.
They look at the way cars are sitting on the road. A strange angle, a rear-end hit, a smashed side door… all those things help them understand the direction and force of each impact.
They check skid marks, which show braking attempts or sudden steering moves. They look at debris because it tells a story too. Broken glass, loose parts, fluid trails – these things basically point to the moment of impact.
They also check environmental stuff. For example, was the road wet? Was the sun blasting right into someone’s eyes? Was there a stop sign that someone blew past?
All of this helps form a picture of how the crash happened.
Also Read: How To Document Evidence After A Car Accident
#2. Taking Statements
Once officers understand the physical layout, they start gathering voices.
They talk to the people involved. They talk to witnesses. They ask simple questions like, “What did you see?” or “What were you doing right before the crash?”
This part can be messy because people are shaken up, confused, or stressed. Some folks forget details. Some mix them up. Some accidentally exaggerate because adrenaline is high. Officers listen for consistency.
They compare what each person says to the things they saw on the ground.
Independent witnesses help a lot.
A random person walking a dog or waiting at a bus stop often gives the clearest story. They have no reason to hide anything or protect anyone.
#3. Reviewing Traffic Laws
Once officers gather the basics, they move on to the rulebook.
If a rule was broken, it usually points to the cause of the crash.
Traffic laws exist to keep everything flowing safely, so even a small slip like rolling through a stop sign or drifting out of a lane, can set off a chain reaction.
Officers look at the exact spot where the crash happened and match it with the laws that apply there. They check signs, lane markings, speed limits, turn restrictions, and who had the legal right to move first.
They also pay attention to anything a driver should have done but didn’t. Things like using headlights at night, signaling a turn, or keeping a safe distance are all part of the picture.
These little details often show the difference between an unavoidable situation and one that someone caused through risky or careless driving.
Also Read: Can You Sue An At-Fault Driver?
#4. Checking Camera Footage
Camera footage is like the golden ticket for officers. It takes all the guessing out of the situation.
When a video exists, it shows everything in real time including things people forget, things people didn’t even notice, and things people sometimes get wrong because adrenaline was high.
Officers look at recordings from traffic lights, nearby shops, houses with doorbell cams, buses that passed by, or even cameras at gas stations.
Dashcams from drivers are a big help too since more people use them now.
Footage can reveal speed, turn signals, braking, and the exact moment two cars crossed paths. It also shows angles and reactions that are impossible to recreate from memory.
The best part is how footage clears up conflicting stories. Two people might swear they saw totally different things. One short clip ends the debate.
It’s clean, neutral, and very hard to argue with.
So if the crash happened in a busy area, police always try to track down any video they can find.
#5. Conducting Field Tests (If Needed)
Field tests are done when officers think a driver might not be fully alert or capable of driving safely. It’s not just alcohol, it can be anything that affects coordination or judgment.
So they use simple tests like walking in a straight line, tracking a moving object with the eyes, or standing on one leg for a few seconds.
If things look more serious, they use devices like breath tests.
These give a quick reading that helps officers understand what’s going on.
The results influence the investigation in a big way because a driver who isn’t fully alert has a higher chance of making a mistake on the road.
Officers also look for signs like slurred speech, slow movements, confusion, or trouble following directions. They note all of this in the report.
#6. Accident Reconstruction
Some crashes are easy to figure out. Others are a complete mess.
In big or complicated crashes, police bring in reconstruction experts. These people basically replay the crash using measurements, angles, math, and sometimes software.
They check how fast cars were moving. They look at the impact points. They map out the motion before, during, and after the hit. It’s very detailed. It feels like something from a forensics TV show, but it’s real work done slowly and carefully.
Reconstruction helps when stories don’t match or when the crash is too severe to understand quickly.
The results can take time, but they’re often extremely accurate.
#7. Issuing A Police Report
Once officers gather everything (photos, notes, statements, measurements, tests) they put it all into a police report. This report usually includes a diagram of the crash, a timeline, and the officer’s conclusion.
Police reports are important.
Insurance companies love them. Lawyers use them. Drivers request them.
They don’t decide the entire case, but they carry a lot of weight.
Sometimes the report clearly states one driver caused the crash. Sometimes it simply lays out the facts for others to interpret. Either way, it’s the official summary of the entire investigation.
Also Read: How Long Does It Take to Get a Police Report?
When Police Cannot Determine Fault
Not every crash has a neat ending. Sometimes the scene has missing details. Sometimes everyone’s stories clash. Sometimes there’s no camera footage, no skid marks, and no independent witnesses.
In those cases, officers may not call fault at all.
They may write an “unable to determine” section in the report.
It sounds disappointing, but it’s honest. The police can’t guess. They only go by what they can prove.
A no-fault determination doesn’t mean nothing happened. It just means the officer doesn’t have enough to blame one person on paper.
Insurance companies then have to figure it out themselves using their own process.
Police Fault Vs Insurance Fault
Police fault and insurance fault can be two totally different things.
Police look at laws, evidence, and the moment of impact. Insurance companies care about risk, damage, and financial responsibility.
They run their own investigation. They look at the police report, but they’re not required to agree with it. They may assign shared fault. They may split the responsibility into percentages. They may even place fault on someone the police didn’t mention.
A driver might get a ticket but still not be held fully responsible by insurance. Or a driver may avoid a ticket but still get blamed by the insurer.
It’s strange, but it happens all the time.
That’s why people often say the police report is just one part of the puzzle.
Final Thoughts
The police determine fault in an accident by following a process.They listen. They compare what they see against the rules. They use tech if they have it. And they put everything into a report.
If you’re ever in a crash, the best thing you can do is stay calm and help the process.
Take your own photos. Get names. Grab contact info. And later, request the police report so you know exactly what they saw.
Fault can be complicated, but understanding the process makes it feel a whole lot less scary.