Divorved my husband 2 years. His health care judgement on my report

I have been divorced for 2 years,I kept my exhusband on my health care plan, He ended up in the hospital never paid his bill I got a judgement put on my credit for 1984.00 in 12/2007 can they due this?
I never knew anything about it until I pulled my credit in 3/2008 .
Do I have to pay this?
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it seems you would to have had knowledge of any judgment. if you were not served papers, and you only had insurance for the man and were not married to him then, I would think you could just dispute the judgment and it would come off. Say not your account
If this does not work i would investgate the court records at what ever court rendered judgment, hopefully the place is close.
i would also call the hospital and confront billing and see if your name may have been used without your knowlegde as a responsible party which is likely since you state it was your insurance.
there might be a possiblilty that your insurance would not pay since you were not married.
In any event i do not believe this should be on your report