Final answer:
The legal defense where both parties' negligence is weighed to determine damage awards is called comparative negligence. The damages are reduced based on each party's percentage of fault.
Step-by-step explanation:
The legal defense that can be used in most states where proportionate damages may be awarded when both the plaintiff and defendant were negligent is called comparative negligence. In cases involving comparative negligence, the court determines the percentage of fault for each party involved in the incident and reduces the damages accordingly. For example, if a plaintiff is found to be 30% at fault for an accident and the defendant 70%, and the total damages are $100,000, the plaintiff would only be awarded $70,000. It is important to note that the specifics of comparative negligence laws can vary from state to state, with some following a pure comparative negligence system, allowing a plaintiff to recover damages even if they are 99% at fault, and others adhering to a modified comparative negligence system, where the plaintiff can only recover if their fault is below a certain threshold, typically 50% or 51%.