When someone gets hurt in a traffic accident, deciding who's at fault is often a difficult task. Of course, there are some accidents in which it’s pretty obvious where to put the blame, but many times it’s not so clear: enter comparative negligence.

Suppose we have two drivers: Abby and Brian. Abby stops at a stop sign and prepares to turn left onto a busier road with no stop sign. She looks both ways multiple times, and decides to make her turn when the road seems to be clear. Meanwhile, Brian barrels down the road 20 miles per hour over the speed limit. He’s unable to slow down and slams into Abby’s car.

Here, both parties share some of the fault: Brian definitely should not have been speeding, but Abby should have been a bit more attentive and cautious before making her turn. So who is responsible?

Comparative Negligence Theories and How They Work

Some states split the blame -- and the responsibility for paying damages -- by using “comparative negligence” theories. These theories say recovery for damages will be reduced by the percentage of fault attributable to them. This situation is often referred to as "apportionment of fault" or "allocation of fault."

Suppose Abby sues Brian and claims that she suffered damages of $100,000. Assume further that the jury finds that Abby's own negligence contributed to the accident by 30 percent and Brian’s negligence contributed by 70 percent. If the jury agrees that damages are worth $100,000, Abby would only be able to recover $70,000 (or $100,000 reduced by 30 percent caused by her own negligence). If, conversely, Abby’s negligence was found to have contributed 70 percent to the accident, she could only recover $30,000 for the 30 percent fault for which Brian was responsible.

This example is true in states that apply a "pure" theory of comparative negligence. Other states have modified comparative negligence principles, permitting a lawsuit only if the plaintiff was less than 50 percent at fault. Comparative negligence (or comparative fault) laws typically fall into one of the following general types:

Pure Contributory Negligence

In states that recognize the pure contributory negligence rule, injured parties may not collect damages if they are as little as one percent to blame for the incident. Only five states follow this legal rule: Alabama, the District of Columbia, Maryland, North Carolina, and Virginia.

Pure Comparative Fault

States recognizing the pure comparative fault rule of accident liability allow parties to collect for damages even if they are 99 percent at fault. However, the amount of damages is limited by the party's actual degree of fault. So if a drunk driver is predominately to blame for an accident, but makes an injury claim because the other driver had a burned out taillight, he or she may collect a minimal amount of damages. Nearly one-third of states follow this rule, including California, Florida, and New York.

Modified Comparative Fault

The majority of states follow the modified comparative fault model, which is split into two distinct categories: the 50 percent bar rule and the 51 percent bar rule. In states following the 50 percent rule (including Colorado and Utah), a party that is 50 percent or more responsible for an accident may not recover any damages. In states adhering to the 51 percent rule, a party may not recover if he or she is 51 percent at fault.

Have Specific Questions About Comparative Negligence? Ask a Lawyer

It's normal to feel overwhelmed by the complexities of negligence law, particularly when you may be at least partially at fault for your injuries. If you're filing a lawsuit, or defending against one, you owe it to yourself to speak with a seasoned car accident lawyer who can provide personalized legal advice and guide you through the lawsuit process.