and this is dateline! this is a tragedy on top of a tragedy now. it happened so quickly. their parents in the backyard spa. their mom in trouble. my dad just panicked. a sudden slip. a fatal fall. you re losing your mother. you re watching her go right in front of you. someone else was watching her. a curious neighbor. it was scary. the look on his face was almost undescribable. what had she seen? was this drowning really an accident? she s got a huge gash on her head, something like that is not consistent with just falling down. a husband and father is suddenly under suspicion. he s crying and we re crying. he said, they think i hurt mom. three daughters stand by their dad, and one prosecutor stands firm. he s holding his wife of almost three decades under the water. my job is to get justice for cristi hall. was it murder? hello and welcome to dateline a young woman peers into her neighbor s yard and sees something for a few mysterious seconds, a