Appeal of a JP court ruling is always de novo in the court court at law if you perfect your appeal tiimely (within 10 days) and post an appeal bond. No grounds are necessary. Search Texas Rules of Civil Procedure 567-574b. You should consider hiring an attorney if you plan to do this.
(Timely) Ask and Ye Shall Receive.
But as Lu Ann mentioned, you may need an attorney as the County Court is a court of record, rules of evidence and procedure will be much more adhered to, and there will likely be a greater expectation of formality in the presentation of your case.
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