Can someone sue for mental anguish, in a civil suit over a 3 year old car accident?

I and someone else (his 8 year old son also) were involved in a car accident almost 3 years ago that was then founded at fault by my estranged husband. Insurance claims were finalized and my husband was put on probation and has to pay restitution for 5 years also. Now, almost to the day, 3 years later, the other party is suing my husband for mental anguish. He has been known to have mental issues prior to accident in 2009 and his child as well. What does my husband need to do first? We don't own property, live on a small income, and are terrified that this is happening. Can the other party win?