Texas Transportation Code - TRANSP § 524.038. Instrument Reliability and Analysis Validity

(a) The reliability of an instrument used to take or analyze a specimen of a person's breath to determine alcohol concentration and the validity of the results of the analysis may be attested to in a proceeding under this subchapter by affidavit from the certified breath test technical supervisor responsible for maintaining and directing the operation of breath test instruments in compliance with department rule.

(b) An affidavit submitted under Subsection (a) must contain statements on:

(c) An affidavit of an expert witness contesting the reliability of the instrument or the results is admissible.

(d) An affidavit from a person whose presence is timely requested under this section is inadmissible if the person fails to appear at a hearing without a showing of good cause.  Otherwise, an affidavit under this section may be submitted in lieu of an appearance at the hearing by the breath test operator, breath test technical supervisor, or expert witness.