Texas Code of Criminal Procedure - CRIM P Art. 11.14. Requisites of petition

1. That the person for whose benefit the application is made is illegally restrained in his liberty, and by whom, naming both parties, if their names are known, or if unknown, designating and describing them;

2. When the party is confined or restrained by virtue of any writ, order or process, or under color of either, a copy shall be annexed to the petition, or it shall be stated that a copy cannot be obtained;

3. When the confinement or restraint is not by virtue of any writ, order or process, the petition may state only that the party is illegally confined or restrained in his liberty;

4. There must be a prayer in the petition for the writ of habeas corpus;  and

5. Oath must be made that the allegations of the petition are true, according to the belief of the petitioner.