my victim's name is jenny crompton. i'm doing first-degree murder. i'm doing a life sentence for it. >> 20 years ago mark smith stabbed his high school sweetheart to death on a hot summer day after school. >> she thought i was cheating on her. i didn't want to hear it. she got pretty emotional, you know, upset. i was getting upset. and with her getting upset made me get even more upset. it just went back and forth. got to pushing, you know. and then she is trying to tell me, well, you better go. you better go. i'm like i really don't care, you know. you're not going to tell me what to do. you are not going to push me around. she went to the kitchen. she come back out with this knife in her hand, right? from the kitchen block that she had in the kitchen, right? what are you going to do with that? you are trying to tell me to get out of the house and you are going to try to scare me out of the house to get me going. it just clicked. something snapped. this ain't gonna happen. this ain't happening. you are not going to do this to me. you know. so she go