A 17-year-old Canoga Park boy was found not guilty of first-degree murder in the strangulation death of his mother and not guilty of the attempted murder of his half-brother. But the Van Nuys Superior Court jury must now consider whether Torran Lee Meier is guilty of second-degree murder or voluntary manslaughter, or innocent of both charges, in the death of his mother, Shirley A. Rizk, 34. Similarly, they must weigh the lesser charges of attempted voluntary manslaughter and assault with force likely to cause great bodily injury in connection with Meier’s half-brother, Rory Rizk, 8. According to testimony, Meier and two friends strangled his mother in October and placed her body in a burning car along with Rory and pushed it over a cliff in Malibu. Meier’s two alleged accomplices, Richard A. Parker, 24, of Antelope Valley, and Matthew A. Jay, 18, of Woodland Hills, will be tried later.