My mother is 74 and needs to file a sworn denial about a debt they say she owes, I was wondering if I can file it for her or does she have to appear at the clerks office herself.
I'm not sure what you mean by "sworn denial." If your mother is being sued for a debt, chances are, she needs to sit down with a lawyer and talk to him or her about it. Parents tend not to talk to children about their debt. It's possible that she DOES owe the debt, it is also possible that if she owes the debt, she may have defenses that she may need to affirmatively assert otherwise they will be waived.
It is also possible that she doesn't owe the debt - and one of the reasons may be that her identity has somehow been compromised. She should check her credit report and see what's there.
If the courts are involved, have your mother speak to an attorney and treat this legal matter with the seriousness it deserves.