GENETIC: Impressed with new DNA technology, county supervisors are poised to vote today for a $200,000 genetic testing lab. . . . Tests of skin, hair or bodily fluid seem a foolproof way to finger criminals, but UC Irvine social scientist William C. Thompson warns against rushing to court with the results. Some labs have taken samples incorrectly or misinterpreted them, he said, and "there's a danger they could convict an innocent person."