My ex is suing me for the same case, can it be reopened/judged again?

He was trying to Sue me for $5k+ in sept 2010. I ended up having to pay $1500. He is suing me again for the rest he wasn't ble to get from the last judgement($3k). This is for a nordstrom credit card he had authorized me as a secondary in the past. Ive never used it again since we've broken up, it was cut and disposed. There's No way to determine if the charges were made by the primary or secondary as said in the policy. Can this trial be qualified for another judgement? He had also emailed me regarding him hitting rock bottom with his DUI & car accident which is one reason he wants money to pay his dues and issues which should be none of my business. The subpeona was given to me barely a week ago, the court date is tomorrow, the 12th. & it was passed person to person to be given to me, the person who signed the given subpoena did not actually give it. Is this valid? What are your views on my situation?