Tex. Code Crim. Proc. art. 39.07

Where depositions are taken under commission in criminal actions, the officer or officers taking the same shall certify that the person deposing is the identical person named in the commission; or, if they cannot certify to the identity of the witness, there shall be an affidavit of some person attached to the deposition proving the identity of such witness, and the officer or officers shall certify that the person making the affidavit is known to them.