## Facts

- Jerry Glenn Reynolds II was charged with misdemeanor driving while intoxicated (DWI).
- Before pleading guilty, Reynolds filed pretrial motions challenging the admissibility of Intoxilyzer 5000 breath-test results.
- The trial court ruled the breath-test results admissible; Reynolds entered a guilty plea conditioned on appealing that ruling.
- The test was administered by a DPS trooper who was a certified Intoxilyzer 5000 operator but had little or no understanding of the scientific principles underlying the device.
- The State presented a certified technical supervisor who understood the science and technology of the Intoxilyzer 5000 and had first-hand knowledge that the device was maintained and in good working order on the test date.
- The court of appeals affirmed; the Court of Criminal Appeals granted discretionary review to address whether operator scientific knowledge is required for admissibility.

## Issues

1. Whether Intoxilyzer breath-test results are inadmissible unless the test operator can demonstrate a working knowledge of the scientific theory behind the device.
2. Whether the State satisfies scientific-evidence reliability requirements when a certified operator conducts the test and a qualified technical supervisor establishes the machine’s reliability and proper maintenance.

## Decision

- The Court of Criminal Appeals affirmed the court of appeals and upheld the admissibility of the breath-test results.
- The court held that the breath-test operator need not understand or be able to explain the scientific theory behind the Intoxilyzer for the results to be admissible.
- The court concluded the State adequately established reliability through operator certification, technical-supervisor testimony, and compliance with Texas scientific-evidence requirements.

## Legal Principles

- Scientific evidence is admissible if the proponent shows (1) the underlying scientific theory is valid, (2) the technique applying the theory is valid, and (3) the technique was properly applied on the occasion in question.
- For breath-test evidence, the “proper application” element may be shown through proof that the operator was properly certified and followed approved procedures, even if the operator lacks scientific understanding of the device.
- A qualified witness, such as a certified technical supervisor with knowledge of the science and responsibility for maintenance and oversight, may establish the reliability of the breath-testing instrument and the testing program.
- Statements in prior decisions suggesting the operator personally must possess a working knowledge of the scientific theory were treated as nonbinding dicta and did not alter the governing rule permitting admission with appropriate supervision and reliability proof.

## Conclusion

The court held that Intoxilyzer breath-test results are admissible when the operator is properly certified and the State establishes reliability under the Texas scientific-evidence standard through qualified supervisory testimony and proof of proper maintenance and procedure, even if the operator cannot explain the underlying science.


Reynolds v. State, 204 S.W.3d 386 (Tex. Crim. App. 2006)