Kelly v. State (Texas CCA 1992)
Kelly v. State (Tex. Crim. App. 1992): Standards for Scientific Evidence in Texas
Courts must ensure expert testimony is based on sound science — not speculation.
Background
Kelly was convicted of DWI based in part on gas chromatography evidence. He challenged the reliability of the forensic method and the expert’s testimony. The case required Texas courts to define when scientific evidence may be admitted under Rule 702 of the Texas Rules of Evidence.
Questions Presented
- What reliability standards govern the admissibility of scientific evidence in Texas?
Majority Opinion — Presiding Judge Michael McCormick
Holding: Scientific evidence must be relevant and reliable, supported by clear proof of proper methodology, testing, and acceptance.
The opinion created the “Kelly factors,” applied by Texas judges when evaluating science:
- Validity of the underlying theory
- Soundness of the technique
- Application of the technique on the occasion in question
In Montgomery County, Kelly challenges commonly target:
- Breath and blood alcohol testing
- Drug recognition evaluations
- DNA mixture interpretation
- Ballistics and toolmark evidence
Forensic science is not infallible. Kelly ensures Texas juries are not misled by flawed experts masquerading as infallible authorities.