## Facts

- A victim was assaulted and raped at night while walking along a poorly lit road; she kept her eyes closed and could not identify the assailant.
- Police recovered a fresh Bel-Aire cigarette butt at the scene and collected semen during a hospital sexual-assault examination.
- A state trooper contacted Donald J. Blasioli during the investigation; he admitted smoking Bel-Aire cigarettes and voluntarily provided a saliva sample, but refused hair and blood samples.
- Testing showed Blasioli had type A blood, consistent with the cigarette-butt evidence; police then obtained a warrant for his blood and hair.
- DNA testing matched Blasioli’s blood to DNA extracted from semen recovered after the assault.
- The prosecution sought to present both the DNA match and statistical testimony quantifying the rarity of the profile using the product rule (and also a ceiling-principle estimate).
- At a Frye hearing, the defense challenged the scientific acceptance and reliability of product-rule calculations and offered an alternative approach yielding a far higher random-match probability.
- The trial court admitted the DNA match evidence and the statistical probabilities; a jury convicted Blasioli of rape and related offenses, and the intermediate appellate court affirmed.

## Issues

1. Whether, under Pennsylvania’s Frye general-acceptance test, expert testimony quantifying random-match probabilities for a DNA profile using the product rule is admissible in a criminal trial.

## Decision

- The Supreme Court of Pennsylvania affirmed.
- The Court held that the product rule for calculating DNA profile frequencies and random-match probabilities is generally accepted in the relevant scientific communities and therefore satisfies Frye.
- The Court ruled that disputes about assumptions, databases, and alternative statistical approaches affect the weight of the evidence, not its admissibility.
- The Court concluded that probability testimony may assist the fact-finder in assessing the significance of a DNA match and is not excluded solely because low probabilities may be powerful.

## Legal Principles

- Pennsylvania applies Frye to novel scientific evidence; admissibility turns on general acceptance of the methodology in the relevant scientific fields, not on whether the court finds the method scientifically “correct.”
- General acceptance may be shown through expert testimony and recognition of the method in relevant scientific and professional communities.
- The existence of disagreement among experts does not bar admission under Frye when the methodology is generally accepted; competing views are for cross-examination and jury evaluation.
- DNA match testimony may be accompanied by population-frequency/random-match statistics when the statistical method (including the product rule) meets Frye and will help the fact-finder understand probative value.

## Conclusion

The court upheld the admission of product-rule DNA probability evidence under Frye, holding that the method is generally accepted in relevant scientific communities and that methodological disputes are for the jury to weigh rather than grounds for exclusion.


Commonwealth v. Blasioli, 713 A.2d 1117 (Pa. 1998)