Investigators have focused on suspect William Balfour's movements on Friday, the day of the murders, as well as his conflicts with his estranged wife, Julia Hudson, and other members of the family. They are trying to determine whether another person drove Balfour to the West Side after the killings at the Hudsons' South Side home, sources said. Witnesses said Balfour drove his teal Chrysler to the Hudsons' block Friday, arriving about 7 a.m. But later the vehicle was discovered by police parked about a mile away outside Robeson High School. Balfour's girlfriend told police that he was at her West Side home not long after the slayings of Hudson's mother, Darnell Donerson, and the Oscar-winning actress' brother, Jason, at their Englewood home, sources said.