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 man a woman and the moment it's unsettling. what she saw and what she did would set in motion a chain of events that would divide a family and a jury. here is keith morrison. >> we know the truth. and we know everything that happened. >> how do we know what we know? >> emotionally unsatisfying not to have that answer. >> so it is. even if we've seen something or we think we have. and that's the question at the heart of the whole puzzle. is this woman right? >> i know what i saw. and i know the conclusion of my story. >> of course she does. of course she does. so why does this other woman think this? >> she doesn't know for sure what she saw. >> a question, we say, on which all the rest will turn. why don't we begin here. calimesa, california, riverside county. historic missions. sprawling suburbs creeping out to the rim of mountains around the eastern flank of

. >> when it was over, hall convicted and sentenced to 25 years to life, some of cristi's relatives metutting him away because he is a murderer. >> and the hall daughters, having lost their beloved mother, fought to save a father they adored, and having lost that fight, aren't quite sure what they'll do now. >> for the family. to say we were close is an understatement, you know. to go from that to being not able to be there with each other. it's -- it's the biggest heartbreak that anyone can ever experience, i think. >> that's all for this edition of "dateline: extra." i'm craig melvin. thank you for watching. >>> this is an msnbc special series. ♪ >> cool. if you could only define it. >> define it would diminish what cool is. >> find it. >> everybody's trying to sell you cool. most of the time it don't work. you can't measure, you can't market. it is what it is. >> catch it. >> i just don't actually think cool exists. i don't think it's actually a thing. >> you could make a killing. >> cool equals dollars. >> sounds like you're off to a good start. >> that's the eternal quest for those