Three rules in three flavors
Five jurisdictions still follow contributory negligence, which bars you from any recovery if you are even 1% at fault: Alabama, Maryland, North Carolina, Virginia, and the District of Columbia.
Pure comparative negligence states reduce your recovery by your percentage of fault but never bar it entirely. A 70%-at-fault plaintiff with $100,000 in damages still recovers $30,000.
Modified comparative negligence states reduce your recovery by your percentage of fault and bar it entirely if you cross a threshold — either 50% (12 states) or 51% (21 states).
Why this matters at intake
Your jurisdiction's rule shapes how aggressively your attorney needs to fight on liability. In contributory and modified-50% states, even a small finding of fault on you is catastrophic — so attorneys spend disproportionate effort proving the defendant's negligence and rebutting any plaintiff fault.
How fault percentages get assigned
Pre-suit, fault is negotiated between attorneys and adjusters based on the police report, witness statements, and reconstruction. In litigation, the jury assigns each party a percentage. Both sides typically retain accident-reconstruction experts in close cases.