I disagree on not needing the cop to be there to witness the accident.

https://i.imgur.com/undefined.jpg

this was my car after a dude in a brand new tacoma t-boned me at a stop sign intersection. i was watching and saw he was really far away and assumed he would slow down. i came to a full stop and started going through the intersection. Because he was going so fast and didn't slow down at all, he closed that distance and hit me.

i'm sure insurance companies have very competent teams to investigate crashes and there is a ton of science and lots of historical data to determine who is at fault in a crash, but I've also heard of times where even when the evidence is in the favor of one party, it isn't quite enough to tip the scale completely in that party's favor and the insurance companies call it a wash and cover each others' claims, with both parties' premiums going up.

When a cop showed up to my crash, he got the story from me and the driver. He told me that based on the damage to my car, there is no way that I was the one that was speeding and he was the one who came to a full stop, because there was no way nor any need for the other driver to get to the speed necessary to inflict that damage on my car in the distance between his stop sign and the middle of the intersection. The officer said he was issuing a citation to the other driver for failing to yield to a stop sign and gave me his business card. I ended up having back injuries that also prevented me from working, and I retained a team of lawyers to recover damages from the other guy's insurance. We were able to get the full $30,000 that was the max liability of the other guy's policy.

Every situation is different and I'm sure an officer could potentially misjudge the scene of the crash and write a report that contradicts "what really happened" and isn't in your favor. But, given the choice I would always choose to have a cop there to give his professional opinion.