## Facts

- David Clarence Pruitt’s automobile struck and killed two pedestrians.
- Police took Pruitt to the station and administered a Breathalyzer test to determine intoxication.
- The device measured alcohol in alveolar (deep lung) air and used a mathematical conversion formula to report a blood-alcohol percentage.
- Officer Ingle administered the test and could follow operating instructions and obtain a numerical result.
- The State did not show that Officer Ingle understood or could explain the scientific relationship between alveolar air readings and blood-alcohol concentration, or the conversion formula used to reach the reported blood-alcohol percentage.
- Over objection, the trial court admitted the Breathalyzer result indicating Pruitt exceeded the legal limit.
- A jury convicted Pruitt of second-degree murder based on the collision.

## Issues

1. Whether a Breathalyzer blood-alcohol result is admissible when the State fails to establish an adequate foundation as to the operator’s qualifications and the scientific basis for converting breath readings into a blood-alcohol percentage.
2. Whether admitting the Breathalyzer result on that showing constituted reversible error in a homicide prosecution.

## Decision

- The Tennessee Supreme Court reversed the conviction and remanded for further proceedings.
- The court held it was error to admit the Breathalyzer result because the State failed to lay a sufficient predicate for the scientific evidence.
- The deficiency was not harmless given the likely weight jurors would give a numerical blood-alcohol figure in a drunk-driving homicide case.

## Legal Principles

- Scientific or technical test results are admissible only after the proponent establishes a proper predicate.
- A proper predicate requires proof of the test’s scientific reliability, that it was properly administered, and that the witness offering the result is qualified and competent to testify to its basis and accuracy.
- When a test’s reported result depends on a scientific relationship or conversion (here, breath alcohol to blood alcohol), a witness must be able to explain or support that relationship; mere ability to operate the device is insufficient.
- If cross-examination shows the offering witness lacks the necessary qualifications or knowledge to support the scientific conclusion, the related testimony should not be admitted (or should be removed from the jury’s consideration).

## Conclusion

The court ordered a new proceeding because the State introduced a Breathalyzer-based blood-alcohol percentage without a qualified foundation establishing the scientific basis for the breath-to-blood conversion and the competency of the witness to support the result’s accuracy.


Pruitt v. State, 216 Tenn. 686, 393 S.W.2d 747 (Tenn. 1965)