this is "nightline." >> tonight, the vanishing and murder of a 3-year-old girl. >> dad! >> hi, i love you. >> i love you! >> she was funny. she was silly. she was just a sweetheart. >> why her father falsely confessed to the crime. >> so you looked at this as your only way out? >> it was my only way out. >> plus connecting the dots. how authorities may have missed early clues. >> one of the things that they found and didn't realized critical importance of it was a pair of shoes. >> and the hunt for the true killer hiding in plain sight. >> all of a sudden my phone started ringing off the hook. i said, this has got to be important.

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hey google, turn up the heat. ♪ ♪ ♪ receive a chargepoint home flex charger or a public charging credit. see you volvo retailer for details. ♪ good evening. thank you for joining us. tonight, a family's heartbreaking loss. a 3-year-old child disappeared and killed. now the relentless hunt for justice by family and authorities, going down a road of twists, turns, and missed

opportunities. here's "20/20" coanchor david muir. >> wilmington, illinois, is the quintessential american small town. >> they were a wonderful family. they were living the dream. it all just shattered. >> what are you doing there? >> kevin fox is your all-american guy. >> melissa and kevin went to high school together. >> they were high school sweethearts. >> we were still dating when god made plans for us and we had tyler. then we got married when he was 3. and had riley a year after that. he was a loving, doting father. >> i feel like that's what i was put on this earth to do, honestly. that's my joy in life. >> riley!

>> he had an especially close relationship with riley, the two of them were inseparable. >> watch where you're going! >> the weekend of june 5th is a turning point in the lives of the fox family. mom goes out of town on a breast cancer walk. >> kevin and my brother tony were going to go to a concert, and my mom had the kids. >> 1:00 a.m., he picks the kids up, brings them home. it's late, so he puts them down in the living room. >> watch tv, i went to bed myself. >> what's the next thing that you remember? >> tyler waking me up and said that riley was gone. >> he gets up. he starts looking frantically all over the house. he thinks that she may be hiding somewhere. he looks in closets. he runs outside.

>> so then i -- started panicking. >> he decides to call the wilmington police department. >> after about 30 or 40 minutes, he calls to say that he can't find his child. >> when police showed up, one of the first things kevin mentioned was the front door, which he remembered having, he thought, closed and locked the night before, and when he got up that morning, that door was open. >> the police stated they found no sign of forcible entry. >> kevin told the investigators s okkevin's wife melissa is stil at the cancer walk in chicago. >> i decided to call kevin. he sounded so startled. i knew immediately something was wrong. he just said, "riley's gone." >> on this day, a lot is happening. not only does riley fox go missing. but the police are responding to a burglary on the very same

block. >> there is a neighbor literally across the street from kevin, she had a section of her screen cut out, the door was unlocked. >> she had felt that someone had broken into her house. >> got to wonder. are these things connected? >> police and the community mounted a massive manhunt. >> 3-year-old riley fox's drowned body was found in a creek about four miles from her home. >> forsythe woods and fort creek suddenly become ground zero for this investigation. the county sheriff's department tasked with leading the investigation. >> there was a logjam furt downstream. that's the location we found the shoe. >> a little while later they come across a matching sneaker. >> they take the tennis shoes, put them in evidence, and that was the end of it. and here's the thing. there's actually something rsoe >> theed at those f the

shoes. >> the child was held under the water. >> mouth taped shut. >> the forensic examination revealed that riley fox was alive at the time she entered the creek. additionally, the autopsy revealed that riley fox suffered nonlethal head injuries and a sexual assault had taken place. >> did a rape kit, they did test for blood, bodily fluids not belonging to riley. >> there were about 20 items that were eventually sent to the fbi for forensic testing. the problem was, there was this enormous backlog at quantico. >> the funeral services were held at st. rose catholic church. 6,000 people showed up. >> within an hour of the funeral ending, police came to myhous and they asked if there was any kevin to be capable of doing

something like this. and before the question even came out of their mouth, my answer was no. >> said, would you please talk to an attorney? no obligation. >> chad felt that the police were focusing on kevin. they kept dropping by the house. >> kevin and i were like, we're fine, what do we need an attorney for? >> reporter: it had been 4 1/2 months since riley disappeared when police say they have a development. >> it's the evening, kevin's been working since 4:30 that morning. they go to the police station. >> they took her down the hallway, they took me -- it was like a room up on a stage. walk up the stairs, then it was real, real small room. >> they had the capacity to videotape the entire interrogation. but they don't. >> and then all of a sudden, out of nowhere, he looked at me and

said, we have reason to believe that you killed riley. i stood up and started pointing at his face saying, you know i didn't do this. >> kevin says detectives offer him a lie detector test. he says, one of the things they tell him is this test could actually prove that he wasn't involved in his daughter's death. >> this is a commonly used ruse during police interrogations. get the suspect to take a lie detector test, then tell them they failed it. as part of that process of breaking them down. of making them feel hopeless. >> i was just shocked. i couldn't have failed it. >> the wilk county sheriff's office says kevin's account of this interrogation is exaggerated, not accurate. >> look, either you're this cold-blooded baby killer, life in prison -- or, if you tell us this was the result of some accident, things will be areas for you. that's how they get kevin talking.

just tell us about an accident. >> keep in mind, he'd been up since 4:30 that morning, gone to work. now this 14-hour interrogation. he confesses to it. >> police construct a theory that he adopts in which riley is killed accidentally, and he then stages it to look like a murder. >> he says, i thought everybody would see it as crazy, he said, i really thought they would understand that this couldn't possibly have happened. >> did you have anything to do with the death of your daughter? >> not at all. not at all. >> a lot of people want to know, if you didn't kill riley, how do you possibly confess to it? >> say you were trapped in a burning room. and there was only one door, and the fire was just flaming around you. >> you looked at this as your only way out? >> it was my only way out. >> gets arrested, gets taken to the wilk county jail and booked. the second he's arrested, chad

goes in, the older brother, retains kathleen zellmer as his attorney. >> kathleen zoellner is one of the best criminal defense attorneys in the country. >> we will see them in court. success comes from her ability to work with dna evidence. >> kathleen zoellner is worried kevin's confession will be enough to convince a jury to convict him. she believes the only way to avoid a guilty verdict is through dna. >> while zoellner's team continued to try to poke holes in the story offered by investigators, zoellner discovered that there actually was dna evidence. >> dna evidence was available in the murder of riley fox last june, but it required sophisticated testing. >> after that dna evidence was sent out to a private lab -- >> test results arrived last night. the dna did not match kevin fox.

>> they came back and said, this is not his dna. we can't tell you whose it is. but we can tell you it's not his. >> kevin fox is free after prosecutors concede there is now considerable doubt about his ut >> psecutors dropped all charges against the wilmington father. >> if you want to take away one thought in this case, do the test before you make the arrest. >> kevin fox is ruled out. this is a game changer. you have to refocus this investigation. the dna proves that you didn't do it. but then the question becomes, who did? oh, it was terrible. i was totally stranded. no tp? nope, empty roll. so what happened? well... we started buying charmin super mega roll. whoa! that's huge! charmin super mega roll is 6 rolls in 1 and lasts so much longer you don't always have to worry about the roll running out. i'm glad you were rescued, dad.

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when kevin fox walked out of the will county jail after being cleared of charges he killed his 3-year-old daughter riley, the investigation essentially went back to square one. >> kevin and melissa fox sued the will county sheriff's detectives who investigated and arrested him and were awarded about $8 million in damages. >> in june of 2009, five years after the death of riley fox, the case gets a jolt of new energy when the fbi sends a team to wilmington and starts an investigation from scratch. >> they took 30 agents and descended on wilmington and did a massive amount of interviews. >> they came across a young lady who told them that she had a suspicion but had no reason other than gut feeling that this

person might have been involved in the murder. >> so the fbi talks to this woman, then "20/20" ends up talking to her as well. she has since died, but at the time she agreed to do the interview as long as we blurred her face. >> i just had a bad feeling about him. and i didn't know who to tell. >> she told us about scott eby. >> who is scott eby? >> an ex-boyfriend of mine. >> just describe him for me. tell me what kind of person he is. >> a creep. >> the summer that riley fox disappeared, scott wayne eby was 33 years old. he'd been married, in and out of prison. he was l wiinonith his mother. it turns out he was living with her one mile from the fox family home. >> they'd had a very peculiar conversation when they were out for a walk together, walking through riley's garden. >> i was saying, i can't believe somebody did that to a sweet

little girl. and he said, oh, that was such a shame, wasn't it. and the way he said it was like -- cold, like he didn't mean it. >> she told us she knew he was incarcerated for sexual assault of a family member. >> scott eby was five hours away, in prison. i asked jeremy, let's go ahead and try to get this guy interviewed. he was very respectful, very responsive to our questions, didn't hesitate, didn't seem nervous. >> he was just trying to kind of collect his thoughts as to why in the world the fbi is here to talk to me and what i should do about that. >> when they left, he got on the phone with his mother on a recorded call. >> what's the matter? >> mom, um -- i don't know how to tell you this. but -- i got an emergency. you got to -- you got to drop everything you're doing and come down here and see me as soon as

you can. >> we went to interview the mom. scott eby's mom. >> fix the rest of my life -- >> you killed somebody? >> you've got to come down here, mom, so i can give you a hug and a kiss for the last time, please. >> "20/20" obtained a recording of an fbi interview with scott eby's mother. >> and he said that he did something horribly, horribly, horribly wrong. >> it's something really, really, really bad? >> yes, it's something really, really, really bad. >> all of a sudden my phone started ringing off the hook from the prison where scott eby is in. >> scott eby had attempted to commit suicide. >> and he has written a letter. >> that was actually addressed to the fbi agents who had spoken with him. >> "this is a confession to

murder." >> then that started a succession of admissions, and finally a videotaped confession. >> i guess i got it into my head to -- to go rob people. >> he told us that he got a thrill out of robbing homes. >> the same night riley disappeared, there was a burglary at the house right across the street. it turned out that eby was the person who had burglarized the home. >> reporter: authorities say eby said he walked from that neighbor's house right to the backdoor of the fox home. that door, you'll remember, had that broken lock. >> went into the living room. that's where the babies were sleeping on the couch. i was getting ready to leave, and i looked back. and i don't know, for some reason, i just -- i fixated on that little girl. >> as eby keeps talking, he describes how he put riley fox

in the trunk of his car and took her to forsythe woods. and his account reveals even more mistakes in the investigation. >> she's looking directly at my face and stuff. and i realize that my mask is no longer on my face. and then i really panic. >> he made that leap from sexually assaulting her to this warped idea in his head that he needed to take her life at that point. >> he decided to take her and drown her in the nearby river. >> and scott eby admits to leaving clues at the scene of that horrific crime. his shoes, his size 12 sneakers. >> tell you the truth, i expected somebody to be coming, talking to me a long time ago, because it had my last name printed on the tongue of the shoe. >> one of the things in looking back at this case all these years later, it's incredible when you realize that scott eby, who killed riley fox, he had an encounter with wilmington police officers just hours later that same day.

>> a pill bottle of oxycodone. i swallowed them. hoping to kill myself. >> and he has all the red flags that they should have picked up on, from the burglary convictions to the suicide attempts to the inquiries about riley. i mean, he did everything but set a siren off at his house, "i'm the guy." >> reporter: scott eby pleaded guilty in 2010. >> given a life sentence and he pled guilty on multiple counts of murder and aggravated criminal sexual assault. >> the truth of the matter is, they'll never get their daughter back. she had an unmistakable bond with her father, whose family never gave up on him and a family that will never forget its little girl. >> dad, i got sticks! >> you got sticks? >> yeah. >> it will forever be devastating and i'll forever have a hole in my heart. but i think because i have suffered such great loss, i see

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