Superior Court Judge Maxine Chesney was chosen to preside over the most important abortion-related trial in California in many years, which opens today. The non-jury trial will determine whether a never-enforced 1987 state law requiring an unmarried minor to obtain consent from a parent or judge for an abortion violates the state Constitution. The law was scheduled to take effect on Jan. 1, 1988, but was blocked three days before that by now-retired San Francisco Superior Court Judge Morton Colvin in response to a suit by doctors and family planning groups. Forty other states have laws requiring parental consent or notification for a minor's abortion. About half are being blocked by courts.