How would I go about researching , precedence cases of elder abuse, undue influence in texas.

The obvious answer is to contact an attorney that specializes in elder abuse. If you're set on researching it yourself you can go to your local library to find specific cases that have addressed your problem. The librarians in the library can probably point you in the right direction. However, be advised that a non-lawyer will not always be aware of what the rulings in those cases mean and whether it is still good law.