Even if the plaintiff has a pre-existing condition, he/she may still be able to claim for damages if the defendant is liable for the present injury that might have aggravated the plaintiff’s previous condition. As stated in the California Civil Jury Instructions 3927:
“3927. Aggravation of Preexisting Condition or Disability”
[Name of plaintiff] is not entitled to damages for any physical or emotional condition that [he/she] had before [name of defendant]’s conduct occurred. However, if [name of plaintiff] had a physical or emotional condition that was made worse by [name of defendant]’s wrongful conduct, you must award damages that will reasonably and fairly compensate [him/her] for the effect on that condition.”
This means that it should be proven that the act or neglect of the defendant is the “proximate cause” of the injury or aggravation to the injury, that if it had not been for such act or neglect, no injury would have occurred.
Injuries that may have aggravated a pre-existing condition could make it a little bit more challenging to claim for damages. There may also be a need for expert testimonies to prove that the present injury made a previous condition worse. That’s why one should work with a lawyer who is an expert in personal injury cases for more information and to be properly represented.