## Facts

- Lawrence Adam Reeves was charged with multiple residential burglaries and sexual assaults against several women in the San Francisco Bay Area.
- Investigators collected biological stains (including semen or suspected semen) from crime scenes and submitted them to the California Department of Justice (DOJ) DNA laboratory for testing.
- The prosecution presented DNA evidence generated using RFLP testing and PCR-based typing, depending on sample quantity and degradation.
- Prosecution experts testified to extremely low random-match probabilities (e.g., one in millions or billions) for the DNA profiles attributed to the perpetrator.
- A defense expert challenged the probative force of the statistics by emphasizing possible laboratory handling and interpretation errors, suggesting an operational error rate potentially in the range of one in hundreds to one in thousands.
- Reeves was convicted of multiple burglary and sex-offense counts and sentenced to a total term of 77 years in prison.

## Issues

1. Whether the trial court erred by admitting DNA random-match probability testimony without requiring the prosecution to establish a quantified overall laboratory error rate as foundational evidence.
2. Whether the DOJ’s RFLP and PCR DNA methods and associated population-frequency statistics satisfied California’s admissibility standard for scientific evidence.
3. Whether technical disputes over statistical implementation (including match windows, binning, and database choices) required exclusion of DNA statistical evidence or instead went to its weight.

## Decision

- The Court of Appeal affirmed the convictions and sentence.
- The court held that the DNA evidence and associated statistical testimony were properly admitted.
- The court rejected a foundational requirement that the prosecution quantify an overall laboratory error rate before presenting random-match probabilities.
- The court concluded that asserted weaknesses in lab practices and statistical implementation were generally for cross-examination and competing expert testimony and typically affected weight, not admissibility.
- The court issued a minor modification while denying rehearing; the judgment remained unchanged.

## Legal Principles

- Forensic DNA evidence (including RFLP and PCR-based typing) is admissible when the underlying methodology is generally accepted, experts are qualified, and proper procedures are shown in the particular case under the applicable California scientific-evidence test.
- Random-match probability expresses the population frequency of a DNA profile and is conceptually distinct from the laboratory’s operational error rate.
- The prosecution is not required, as a prerequisite to admissibility, to present a single quantified laboratory error rate to accompany DNA random-match probability testimony.
- Claims of possible contamination, mislabeling, interpretation mistakes, or methodological disagreements about statistical techniques are ordinarily addressed through cross-examination and opposing experts and go to the weight of the evidence.
- Courts may admit DNA statistical evidence despite technical criticism where the method is scientifically defensible; evidentiary balancing does not require exclusion merely because the numbers are very small if the defense can present competing explanations.

## Conclusion

The appellate court upheld the admission of RFLP and PCR DNA evidence and accompanying population-frequency statistics, ruling that the prosecution need not establish a quantified laboratory error rate to introduce random-match probabilities and that most objections to operational error and statistical implementation are matters for the jury in assessing weight rather than grounds for exclusion.


People v. Reeves, 91 Cal. App. 4th 14, 109 Cal. Rptr. 2d 728 (Cal. Ct. App. 2001)