The Venegas Decision

On May 11, 1998 the California Supreme Court issued an opinion in the Venegas case in which they affirmed the appellate court's decision to reverse Venegas' conviction.

The case

Venegas, a handyman, was convicted of a rape that occurred at the Red Lion Inn in Bakersfield, on November 2, 1989. The conviction was largely based on DNA evidence.


This opinion is not as disturbing as I first feared.

As I read it, the court rejected the RFLP frequency computations in Venegas on rather narrow grounds. The court did not buy into the 1992 NRC report hook line and sinker. (What a disaster THAT would be, with the bizarre procedures for mixed stains, and for database searches, not to mention the "modified ceiling principle"!)

The opinion does look favorably on the "modified ceiling principle", inasmuch as it appeared to the court that the various experts at least grudgingly admit, with respect to this method, that it probably is fair to the accused.

However, I didn't see that the opinion closes the door on any other fair or correct method of calculation -- such as appropriate floating bins combined with some method of taking heed of possible population substructure (whether by a "theta" adjustment, or by minimum allele counts).

The problem with Venegas is that the modified ceiling principle was applied ala FBI, which is to say incorrectly. Mueller pointed out that using a +-2.5% floating bin is just not good enough when the matching rule is in effect +-5% (because the rule is that two bands may match if they are each within 2.5% of a common neighbor). The court seemed to understand this point quite well. With regard to further sophistry on Mueller's part, the court was properly not impressed.

The part of the opinion that I found the most interesting is the court's explanation and argument that the method of calculation is a matter for a Kelly-Frye hearing, not for the jury to judge. The trial court is held to err in this respect, and the supreme court therefore upholds the appellate court's decision to reverse.

At 64 pages it seems rather wordy, and I was not so entranced as to read every word. Therefore I will enjoy hearing contrary opinions by others who read the Venegas decision differently than I did. Me, I like it. Good job Justice Baxter.

Contrary opinions? Insights? Hate mail?

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