Reporter: Lottie spencer's stalker has taken over her life, and now he is about to take something else from her. I get a call from my daughter. She is so hysterical, and she is screaming that... See More
Reporter: Lottie spencer's stalker has taken over her life, and now he is about to take something else from her. I get a call from my daughter. She is so hysterical, and she is screaming that something happened to nicholas. Reporter: Nicholas smith, then a 5-year-old living with his mom karmen downstairs from lottie and her 10-year-old daughter. The little boy is about to become a victim. I had come home from school and my mom's car was in the driveway. And I just assumed that she was there, so I went downstairs. Reporter: Waiting there is lottie's stalker, waseem daker with a knife in his hand. Mr. Daker grabbed me and started stabbing me. Reporter: What do you feel when you remember what he did to you? Confusion kind of. I don't really understand how someone would do that. Reporter: How did he leave, how did it stop? He was stabbing me and i started yelling for christina's name cause she was down the hall. And he covered my mouth so that I couldn't yell to her. And after he stabbed me a bunch, I couldn't make out who exactly it was. And then I got itch. I didn't know what was happening and then I fainted. Reporter: Lottie rushes home to find the unimaginable. I just saw blood and then i heard sirens and ran to my daughter and there was nick and he was covered in blood. Reporter: Seeing nick stabbed 18 times, lottie flies into a panic. Where's karmen? Where's karmen? You teed to check on karmen. And I knew that, oh, my god. Just the look that they had they said that she was dead. And I just, I didn't even want to believe 'em. I said, "i need to see, she's not dead, and I just need to see." Reporter: Inside police find signs of torture and murder. Karmen smith is in her bed gagged, stabbed, choked to death. Detective john dawes describes a death scene reminiscent of hannibal lecter's. She had marks on her body which indicated she had at one time been handcuffed. She had ligature marks on her throat. She had some bruising. She had two punctures in her back. Her clothing was in such a state that it was apparent she had been undressed and then redressed. Reporter: Did you have any question about who would've done this? No. I didn't want it to be him. There's a lot of guilt that comes with that because you always think, if I would've said this or done that, or -- you can play the what if game, forever. Maybe nick wouldn't be stabbed 18 times. I didn't want it to be him, but it was, I knew. Reporter: The local news shows up to cover the crime that seems so random and cruel, catching karmen's sister who immediately thinks of daker. She supposedly had a restraining order on him or something! This cannot be true! This cannot have happened! Reporter: Within hours, police pick up waseem daker. He denies being in the home. With no good eyewitnesses or physical evidence linking daker to the crime, police can't charge him with murder. Instead, they prosecute him for an earlier charge of stalking lottie. Daker is tried and convicted. But not much consolation for lottie spencer. He gets the ten years. It's not enough. It's not enough. I knew that he killed karmen. Ten years is not enough for anybody for what he did to her. Reporter: Lottie's life is frozen in that moment of guilt and fear. She flees to south carolina but can't escape the traumatic memories. All those years it haunts you because he told you that he could get away with the perfect murder. Reporter: How'd you deal with that? Throughout the years, october is a pretty bad month because of what happened to karmen and nick. Then november comes around, and then you think, "oh, it's thanksgiving and karmen's not there to share it with nick." There's not like a month that can go by, without you thinking about how her family and her son has had to endure. Reporter: Simple tasks like showering or vacuuming now frighten her. Scared the sound will mask someone eaking up behind her. I was pretty broken and started doing drugs to shield the pain. I didn't want to think about anything. It was too painful and too hard. eporter: DID YOU STAY IN Touch with nick? No. Reporter: It was too hard. Unbearable. Very, very difficult. I felt guilty. Reporter: After seven weeks in the hospital, smith's 5-year-old son nik begins a long road to recovery now being raised by his father and aunt. You grew up all those years with no closure. Right? Correct. I was scared 'cause I didn't exactly know if I was safe. Reporter: Meanwhile, that ten-year sentence daker is serving begins to quickly tick down and in 2006 he is released from prison. What does that mean to you at that time? I was scared. Is he angry that he's been in jail? Is he gonna come after me? Is he gonna try to finish what he started? I didn't really know what to think. Reporter: Do you think he's going to come after you when he gets out in 2006? Yes. He's going to come after me and my daughter because he had made threats that he would come after us, my grandchildren, future children. So, yes, of course. Reporter: Did he reach out to you at all? No. Reporter: Did you feel his presence? Yes. Reporter: But while lottie and nick are dreading daker's release, authorities are moving on the case. The passage of time has given them new tools, namely nuclear dna testing. We certainly strongly suspected that this was our murderer, and as we got closer to him being released from the prison system, yeah, I think there was a new sense of urgency Reporter: It turns out a number of hairs had been preserved found under the shirt of karmen smith's lifeless body. They are sent to the lab. The results will change everything. This is beyond a reasonable doubt. This is absolute proof positive that waseem daker was in contact with karmen smith. Reporter:15 years after the death of karmen smith, waseem daker's story that he had never been in the house is disproved, and he will finally stand trial for murder. You get a call. What did they tell you? They got daker. They got him. You're glad that he didn't get away with the murder, but then again, I have to deal with a lot of stuff. I have to deal with all the things that happened back then because now I have to testify.
This transcript has been automatically generated and may not be 100% accurate.