People v. Stevey
209 Cal. App. 4th 1400
Cal. Ct. App.2012Background
- Stevey was convicted of sex crimes against a 16-year-old victim and challenged DNA testimony as a 'new scientific technique' under Kelly.
- Court held Kelly prong-one applies to new techniques; here prosecution did not offer new science, and no defense expert challenged methodologies.
- DNA evidence involved mixed-source samples: pubic hairs (Y-STR/STR) and a breast swab; RFU thresholds affected allele identification.
- Y-STR testing used to resolve male DNA in mixed samples; counted frequencies with a database and a conservative confidence interval.
- Breast swab yielded a partial profile; probabilistic calculations excluded/shared alleles; interpretation relied on peak heights and statistical methods.
- Trial court admitted the evidence and held no Kelly prong-one hearing was required; appellate court affirmed the judgment.
Issues
| Issue | Plaintiff's Argument | Defendant's Argument | Held |
|---|---|---|---|
| Whether Kelly prong-one hearing required for Y-STR/mixed DNA | Stevey: Y-STR/mixed DNA is a new technique needing hearing | Stevey: methodology not generally accepted | No Kelly hearing required; not a new technique |
| Whether RFU-based peak interpretation is a new technique needing Kelly review | Kelly hearing required for interpretation methods | Interpretation is established practice, not new | Not a new technique; admissible under existing practice |
| Whether the database, confidence factor, and exclusion of shared alleles are generally accepted | Methods are generally accepted and conservatively applied | Methods lack national standards benchmark | Methods generally accepted; admissible |
Key Cases Cited
- People v. Kelly, 17 Cal.3d 24 (Cal. 1976) (three-prong test for new scientific techniques)
- People v. Morganti, 43 Cal.App.4th 643 (Cal. App. 1996) (general-acceptance standard; mixed-source DNA considerations)
- People v. Venegas, 18 Cal.4th 47 (Cal. 1998) (probability calculations; match significance in DNA evidence)
- Nelson, 43 Cal.App.4th 1242 (Cal. App. 2008) (product rule; general acceptance of techniques in varied contexts)
- People v. Smith, 107 Cal.App.4th 646 (Cal. App. 2003) (PCR/STR text in mixed-source samples; no Kelly hearing required)
- People v. Hill, 89 Cal.App.4th 48 (Cal. App. 2001) (general acceptance of DNA methodologies (PCR/STR))
- People v. Axell, 235 Cal.App.3d 836 (Cal. App. 1991) (early acceptance of DNA for forensic purposes)