"There's definitely a lot more to the story" says man charged in fiancée's fatal fall from cliff

Did an aspiring model jump off a mountain cliff or was she pushed? The man accused of killing her reveals what may have happened in a new interview with "48 Hours"

Produced by Susan Mallie and Jen Terker

Stephen Nichols was accused of pushing his fiancée to her death off a dangerous hiking trail in 2009. It's a story "48 Hours" has been following since 2015. But the case took a bizarre turn with an outcome no one saw coming and an interview that left correspondent Peter Van Sant asking, what really did happen to Rhonda Casto along the Oregon's Eagle Creek trail?


For defense attorney Mike Arnold,representing Stephen Nichols gives new meaning to the phrase "full-time job."

Mike Arnold: When you have a case where someone's falsely accused, you can't really separate yourself from work and home life. … So while I'd prefer to be coming home and doing farm chores and listen to wildlife … instead I'll be thinking about my closing argument or what the next step of the case is.

Nichols was arrested for murder in February 2015, accused of pushing his girlfriend Rhonda Casto off a trail in Oregon six years earlier.

Judge John Olsen: To that charge, what's your plea?

Stephen Nichols: Not guilty.

Bail was set at $2 million. Nichols would spend the next 14 months in jail awaiting trial.

Stephen Nichols: I try to just take it one day at a time. I read a lot. Play chess. …But really, when it comes down to it, I miss my daughter. …So that's the hardest part.

But in April 2016, with a trial date nowhere in sight, Judge John Olson reduced Nichols' bail to $250,000. Over the next two days, Arnold set out on a frantic mission to gather the 10 percent needed in cash to free his client.

Mike Arnold: People have taken off work to be there to get him out. So it sounds like a small price to pay to be there for when my client gets to see freedom for the first time in a year. …So wish us luck.

But Arnold would need more than luck. He'd need an extra day to arrange for the ankle monitor required for Nichols' release.

Mike Arnold [with cash in hand in front of bail machine]: Presumption of innocence, ladies and gentlemen.

The next day, Arnold feeds the cash into the bail machine.

Mike Arnold: I'm very excited to see Steve for the first time outside in the fresh air.

Two more hours and Arnold gets his wish.

Stephen Nichols: I wanna cry actually, I'm so happy. But it's a bittersweet victory. …We will continue to fight until we have proven my innocence.

Mike Arnold: It's still a long fight ahead. But now I've got him out with me so we can work on this as a team … so this is a big deal.

But how exactly did Nichols and his attorney end up at this moment? It all started 11 years earlier when a stunning 20-year-old woman knocked on Nichols' bedroom door at his home just outside Portland, Oregon.

Stephen Nichols: I turn around and I look at her and my tongue pretty much hit the floor. …Up until that point she's the most beautiful woman I have ever seen. And she's like, "Hi. My name is Rhonda."

In 2005, Nichols, who was 10 years older than Rhonda and recently divorced, was working as a day trader.

Stephen Nichols: I had a three-bedroom condo and the other two rooms were just empty.

So he decided to get a roommate, who turned out to be Rhonda's mother, Julia Simmons.

Julia Simmons: I first met Stephen Nichols through the internet. I was looking for a place, a room to rent.

Julia Simmons: He can be very charming. …and you know, somebody that's really nice.

Rhonda's best friend, Jessica Colburn, wasn't surprised Stephen was instantly attracted to Rhonda, who was an aspiring model.

Rhonda Casto

Jessica Colburn

Peter Van Sant [holding a photo of Rhonda]: Tell me about this.

Jessica Colburn: That was part of her modeling portfolio. I just love it because she just looks amazing in all of those pictures.

Stephen Nichols: Everything about her was impressive. And I just immediately fell in love with her.

Peter Van Sant: And what were you sensing from Rhonda?

Stephen Nichols: I felt she was into me too. I could tell that she valued intelligence and I've always thought that that's one of my strongest assets.

Julia Simmons: I think she was attracted not so much to his looks, but to his – his — what he had. His condo, his money, his — you know, his status.

Soon, Rhonda joined her mother in the condo, not as a roommate but as Nichols' girlfriend. Rhonda's younger sister, Tessa, was just nine years old at the time.

Tessa Simmons: When I first met Steve … he was really fun. Because I was a little girl, he was playful, you know.

Three years into their relationship, Rhonda and Nichols — living together but not married — became parents.

Casto, Nichols, and daughter

Rhonda Casto and Stephen Nichols with their infant daughter in a holiday photo

Rhonda Casto/Facebook

Stephen Nichols: When our daughter was born, it meant everything to her. …She became the focus and the center of her life.

Tessa Simmons: I loved having a niece. …I was always over there. …And she loved playing with jewelry, just like Rhonda did.

Rhonda loved being a mom, but hoped to restart her modeling career.

Stephen Nichols: She had gained quite a bit of weight from having our daughter. …She was the heaviest she had ever been, and she felt really disgusting.

So Nichols says the couple came up with an adventurous plan to lose weight.

Stephen Nichols: We made it a pact that we would hike … 20 or 25 of the top trails in Oregon. …We'll just start crossing 'em off the list.

But Jessica Colburn says Rhonda told her about only one planned hike.

Jessica Colburn: She was so happy that he was finally planning something. In all the years they had been together, he had never put any effort into planning anything for her.

Including those plans to get married.

Jessica Colburn: The proposal never happened. …Things were tough after the baby was born. He wasn't around as much. I think she held on for longer for the sake of the baby.

Colburn says Rhonda had grown unhappy and that the relationship had taken a dangerous turn.

Jessica Colburn: She told me that he had — in the recent months — been physically abusive to her.

But Nichols claims just the opposite was true.

Stephen Nichols: We wouldn't argue at all. …We were spending a lot of time together. …So I would think that would be the closest that we ever were.

Stephen Nichols: We planned on getting married in the summer. That was my timetable.

Peter Van Sant: So when Stephen is telling us that they were planning their future together and everything was great and it was a lovey-dovey relationship, is he lying to me?

Jessica Colburn: He's absolutely lying to you. I — I've witnessed their fights. I was on the phone a couple of times when they were in a physical fight, actually.

And Julia Simmons claims Rhonda made a chilling statement to her just before the hike.

Julia Simmons: She says, "He's either gonna give me a ring or he's gonna throw me off the cliff."

On March 16, 2009, Rhonda and Stephen would set out on that fitness hike and Rhonda would not live to see the end of the day.


Three months after Stephen Nichols' arrest in 2015, his attorney, Mike Arnold, took his own investigative team up the Eagle Creek Trail where, he believes, Rhonda Casto slipped and fell to her death.


Mike Arnold and an investigator at the spot where Rhonda Casto fell to her death

Mike Arnold: This is probably the most hiked area in the Columbia River Gorge for several reasons. One, the sheer beauty of the hike.

Mike Arnold: Inclement weather hits and disaster happens.

Mike Arnold: Between the physical evidence and the science, there won't be much dispute about this bein' — a tragic accident on a dangerous trail.

Stephen Nichols says this is how the tragedy unfolded: they were heading down the trail, Rhonda is in a great mood and jokingly she had put a towel around her shoulders and was calling herself Supergirl. She broke into a run and, according to Nichols, she slipped on the wet path and fell more than 150 feet to her death.

That was his story in 2015, when Nichols was forbidden by his attorney from discussing details of Rhonda's deadly fall with "48 Hours""

Stephen Nichols: I'm not going to comment on that.

Until now, his only account was the one he gave to police the day of the tragedy.

Stephen Nichols: Again, something I'm not going to comment on…

But in 2017, Stephen Nichols broke that silence.

Stephen Nichols: Either I pushed her, she jumped of her own accord or she slipped.

He sat down and spoke to "48 Hours" about the day Rhonda Casto died.

Peter Van Sant: Let's get in that time machine and go back to March 16, 2009.

Stephen Nichols: We woke up early.

Nichols says Rhonda seemed focused on the future as they drove to Eagle Creek Trail.

Stephen Nichols: She says, "I desperately need to lose weight, because they want to use me as the Maria Sharapova lookalike model." And I'm like, "Yeah you really do look like her."

But then, Nichols claims, Rhonda asked him a startling question completely out of the blue.

Stephen Nichols: She said, "If anything ever happens to me, would you promise to watch our daughter and take care of her?" And I said, "Of course."

Stephen Nichols: And I go, "What are you talking about?" She goes, "I have dreams all the time." …"that I am dead by 25."

Nichols says the question unnerved him, especially since three months earlier, he claims Rhonda had demanded he buy life insurance.

Stephen Nichols: She was adamant about it. …I said, "Why do you want this life insurance?" And she goes, "Because I wanna leave our daughter something in case I die."

So both Nichols and Rhonda had each taken out a $1 million policy on the other.

Julia Simmons: He planned the whole thing, it was premeditated, the whole thing.

Rhonda's mother doesn't believe a word of Nichols' story, saying the insurance was all his idea and that Nichols, the day trader, had an ulterior motive.

Julia Simmons: He had lost a bunch of money the year before. He lost like a quarter of a million dollars. …Using insurance, and then four months later she's dead.

The couple got to the trailhead, where Rhonda snapped a photo of Stephen, later found on her cellphone.


Rhonda snapped a photo of Stephen, which was later found on her cellphone.

Stephen Nichols: The weather was excellent, actually.

But Nichols says Rhonda was acting strangely.

Stephen Nichols: And I asked her … "Are you OK hiking on this trail?" …And she goes, "I used to come up here with a bottle of vodka and a bag of weed." She goes, "I'll be fine." So I said, "OK."

They hiked up a few miles.

Stephen Nichols: I remember we kissed for a little bit. I remember she wanted to have sex. …I said, "No." Like, I'm very prim and proper. I didn't wanna do that.

Then, Nichols says, Rhonda once again asked him that unsettling question.

Stephen Nichols: She asked me if anything ever happened to her would I promise to take care of her daughter.

But Rhonda may have been thinking about more than their daughter.

Peter Van Sant: What are you saying, Stephen?

Stephen Nichols: I mean, I think anyone with an ounce of intelligence can fill in the blanks. You would have to look into how many times in her past she committed suicide.

Peter Van Sant: Attempted suicide.

Stephen Nichols: Yeah, of course.

Nichols says Rhonda was depressed and, shockingly, that she had tried to take her own life at least three times before he even met her.

Julia Simmons: [Laughs] She's never attempted suicide. Never. …He's lying. …But you know what? People that have to make up lies are, you know, you can obviously tell that they're guilty.

And there's more. Nichols claims that Rhonda had long struggled with a serious drug problem.

Stephen Nichols: She's never been off drugs since the age of 12.

Peter Van Sant: What kind of drugs?

Stephen Nichols: Everything. Everything.

Peter Van Sant: Alcohol, cocaine?

Stephen Nichols: All of em.

Peter Van Sant: Marijuana? Crystal meth?

Stephen Nichols: All of 'em. Heroin.

But Rhonda's autopsy would show that she only had traces of marijuana as well as prescription drugs for anxiety and depression in her system. Jessica Colburn says Rhonda did suffer from postpartum depression.

Jessica Colburn: She was in therapy. And sh — that's why she was on the prescription medications.

Nichols says they didn't linger on the trail for long.

Peter Van Sant: And who decides, "Hey, let's head back?"

Investigating the death of Rhonda Casto
12 Photos

Investigating the death of Rhonda Casto

The young Oregon mother and aspiring model fell to her death during a hike with her fiancé in 2009

Stephen Nichols: It was decided by the weather. It started pouring down rain and thunder came. And so she just started bolting down, like at a full sprint, running down the trail.

Peter Van Sant: Now, I've been on that trail. It's a narrow trail.

Stephen Nichols: It is very narrow.

Peter Van Sant: Did you yell at her, "Hey, what are you doin', stop, walk, we're walking down?"

Stephen Nichols: I don't think I screamed anything at her.

Nichols says the steep trail became slick.

Stephen Nichols: I hugged the right wall pretty much on the way down. …This is cascading rain, like, you can actually just see the water flowing down the trail.

Peter Van Sant: So take me to the time of the fall. What do you remember?

Stephen Nichols: [Laughs] That part I'm not gonna take you through, because she did fall off, and I can say I had absolutely nothing to do, either directly or indirectly, with her falling off.

But what Nichols seems to be suggesting to "48 Hours" is that Rhonda may have chosen to go off that cliff.

Peter Van Sant: Did she take a step and her feet went out in front of her? Did she tumble forward? What did you see?

Stephen Nichols: Next question.

Peter Van Sant: Was there a large skid mark on the — on the path where she had slipped and went off?

Stephen Nichols: No. There's just a footprint.

Peter Van Sant: Just a footprint.

Stephen Nichols: Uh-huh. [Pauses, looks away from Van Sant]

Peter Van Sant: Steve, look at me. What you're saying is she jumped. She was going down at– almost a run pace. There's a single footprint, you're telling me, at the edge of the cliff. And she goes over. That's a jump.

Stephen Nichols: I've laid everything out there. People can reach whatever conclusion they want.


Stephen Nichols: She did fall off. And I can say I had absolutely nothing to do either directly or indirectly with her falling off.

Stephen Nichols: There's definitely a lot more to the story. But I'm not going to say it.

While not saying it in so many words, Stephen Nichols' mind games manage to drop a bombshell.

Peter Van Sant: You've led me down a path to believe this was a suicide, and I don't think you can look me in the eye and say, "Well, Peter, you're wrong," can you?"

Stephen Nichols [looks away as he responds]: No.

Suggesting that Rhonda Casto chose to jump to her death from Eagle Creek Trail.

Stephen Nichols: What was her point in going up there? …How to say this. She knew she wasn't livin' past the age of 25. [Laughs] …she knew that for a reason. …She just wasn't a happy person. And she thought that having our daughter would bring her happiness and it didn't.

Julia Simmons: She had a 9-month-old baby at home that she loved dearly. And she loved her family. …So that's just another one of his lies … to take the heat off of himself.

After Rhonda went off the trail, Nichols says he hiked down the deep ravine.

Peter Van Sant: What'd you do when you got to her?

Stephen Nichols: Well … I held her. That's the first thing I did when I got there.

With no cell service to call for help, Nichols says he made his way back to the trailhead and dialed 911.

Stephen Nichols: The police never once asked me if it was a suicide. They never even brought it up, suicide. …I just answered the questions that they asked.

Peter Van Sant: Why didn't you tell them back in the day that suicide was something she was contemplating?

Stephen Nichols: Would it have made a difference, do you really think?

Nichols may have had a million reasons to keep suicide a secret.

Stephen Nichols: If it's a suicide, life insurance doesn't pay out. So our daughter would have gotten nothing.

Is Nichols being self-sacrificing, having said nothing about suicide until now — even as he stands charged with murder — or is he self-serving?

Julia Simmons: I think Steve is just throwing all these ideas out to throw people off the fact that he pushed her. …"Oh, well, she killed herself because she wanted to make a better life for her daughter."

An investigation into Rhonda's death was immediately launched and a memorial was held.

Peter Van Sant: Rhonda's family claims that you were not grieving. …You seemed unmoved by Rhonda's death.

Stephen Nichols: The exact opposite. I was crying nonstop. When I'm really, really sad, I just — I close down. It's just the way I deal with pain.

Shortly afterward, Nichols moved across the state with his daughter to live with family.

Stephen Nichols: For about three months after Rhonda died, I completely shut down.

By 2013, four years had gone by and no charges had been filed against Nichols. He decided to start a new life in a new land.

Peter Van Sant: So how does a kid from Oregon end up in China?

Stephen Nichols: I had been there before. … And I liked China.

Nichols packed up and headed to Wuxi, about 75 miles from Shanghai.

Stephen Nichols: I decided when I got to China, this is a whole fresh start. I was like, "F— America. F— all the past."

Stephen Nichols: I was tellin' my daughter … "This is our new life. Let's make it work."

Nichols got a job teaching English to Chinese businessmen.

Stephen Nichols: My daughter was absolutely thriving. …A little over two months and she was fluent in Mandarin. She had dance lessons. She was taking Tae Kwon Do. She was learning to play the piano.

He began to thrive too, falling in love with Landy Yin Yan.

Landy Yin Yan and Stephen Nichols

Landy Yin Yan and Stephen Nichols

Stephen Nichols: She's beautiful, of course. But she's the deepest, funniest person I've ever met.

Nichols says Landy became like a mother to his daughter.

Stephen Nichols: I can say this with being with so many American women, Chinese women — all-inclusive — are better partners. …It sounds so insulting to American women [laughs], but they just — they make better partners. They make better wives.

And so Nichols decided to make Landy his wife after a year of dating.

Stephen Nichols: I had actually proposed to her right before I came back to America.

Nichols flew back to the U.S. with his daughter in February 2015 to get married. Landy would follow a few days later.

Stephen Nichols: We were planning on getting married both in America and China to make it official.

What Nichols didn't know is that the entire time he was out of the country, investigators stayed on Rhonda's case and Simmons stayed on theirs.

Julia Simmons: I kept calling and asking why anything — nothing was happening.

But something did happen. In April 2014, a secret grand jury heard evidence and indicted Nichols for the murder of Rhonda Casto. So 10 months later, when Nichols and his daughter arrived in San Francisco…

Stephen Nichols: They said something was wrong with my bags. I was like, "That's interesting."

Instead of catching his connecting flight to Oregon, Nichols says authorities separated him from his daughter.

Stephen Nichols: I'm like, "What is going on here? Something's fishy." And then yeah, that's when they arrested me. And I could hear my daughter in the other room, crying. And she goes, "I wanna be back with my dad."

Stephen Nichols booking photo

Stephen Nichols booking photo

Nichols would be extradited to Oregon and his daughter would be sent to live with Rhonda's family.

Stephen Nichols: I was shocked. …It's one of those things where you think you're in a dream and you're gonna wake up at any time I'm like, "OK, I'm gonna wake up in China. My daughter will be nudging me and we'll be back to normal." But that never happened.

Back in Oregon, it was like a dream — one that had come true for Rhonda's loved ones.

Julia Simmons: I just busted out crying. …It was amazing. I couldn't believe it. I was just like, "After all this time, finally."


For months following his February 2015 arrest for murder, Stephen Nichols faced pretrial hearings on a slew of issues from evidence to motive — including whether there should even bea trial since the defense considers Rhonda Casto's death an accident.

Both sides called witnesses:

Prosecutor Carrie Rasmussen: Was this immediately investigated as a murder?

Sheriff Matt English | Hood River County: No.

Mike Arnold | Defense attorney: And when did it become … a homicide investigation as opposed to an accidental fall?

Gerry Tiffany | Lead investigator: Pretty much the next morning.

Medical examiner and forensic pathologist Dr. Christopher Young says Rhonda's injuries were mostly below the waist.

Dr. Christopher Young [in court]: I can tell that — based on the injuries that she has, she — she landed — predominantly on her legs and her pelvis.

Dr. Christopher Young [in court]: The pelvis was essentially shattered.

The defense argues the location of her injuries indicate Rhonda left the trail feet first not tumbling head over heels from a push. It's a theory that could support Nichols' new suggestion of suicide.

Carrie Rasmussen [in court]: When you look at the relationship that the defendant then had with Rhonda Casto…

Notes from a therapist Rhonda had been seeing reveal she was depressed but not suicidal from her relationship with Stephen, which she described as "loveless."

Carrie Rasmussen [in court]: What the state has to prove in this case is the defendant did a criminal act.

Prosecutors hope the judge will allow them to tell jurors about some "bad acts" in Stephen Nichols' troubled past at his upcoming murder trial.

Mike Arnold [in court]: It is something that obviously is titillating and interesting.

The first one, a shocking love triangle involving another of Rhonda's younger sisters, Melanie, that may have provided a motive for murder.

Peter Van Sant: Do you believe that Stephen was in love with Melanie?

Jessica Colburn | Rhonda's friend: Yes. I do.

Colburn says Rhonda learned that Nichols was having sex with Melanie.

Peter Van Sant: And did Rhonda ever tell you how young her sister was when she first had sex with Stephen?

Jessica Colburn: She was 15.

Peter Van Sant: Fifteen years old

Jessica Colburn: Yes.

In fact, just after his arrest for murder, Nichols was indicted on two counts of third-degree rape and three counts of third-degree sodomy for allegedly having sexual relations with an underage Melanie back in 2005.

Julia Simmons: He did rape my daughter. …And I didn't wanna believe it.

In October 2016 while awaiting his murder trial…

Peter Van Sant [to Nichols]: You agreed to plead guilty to two counts of sexual abuse with Melanie Casto. And you signed your name under this statement: "I had sexual intercourse with Melanie Casto. Twice."

Nichols insists his admission was false.

Peter Van Sant: Did you have sex with her?

Stephen Nichols: No. …I'm like, "Well, can I take a plea and then just say, obviously it never happened," and — I was told later, nope. In order to pass the sex offender treatment, you have to admit that.

Even though he'd be a registered sex offender, the law would allow Nichols to still fight and regain custody of his daughter, who was in the care of the state.

Stephen Nichols: I became desperate. I wanted my daughter back.

Stephen Nichols: You'll be amazed at what you're willing to sign to stay out of prison.

But investigators believe there really was a relationship between Nichols and Melanie, one that continued on and off for four years, right up to that fateful last hike. Just a few hours before her death, Rhonda, who had learned of the affair, sent this text to her sister:

Peter Van Sant [reads text aloud to Nichols]: "I don't know what to say besides he's a piece of sh–. He used you to hurt me. I won't let him screw us up again. … When you need me I am waiting."

Peter Van Sant: This Rhonda sounds like somebody who doesn't care much at all about you. She's angry with you.

Stephen Nichols: Does sound like she's angry. I have no idea why she sent those.

But Simmons says she knows why.

Julia Simmons: She loved her sister. And she knew that Steve was trying to drive a wedge between 'em. And she — I guess she figured it all out, and realized what he was doing.

Carrie Rasmussen [in court]: On the night of Rhonda Casto's death, the defendant didn't run to where his daughter was. Didn't run to his parents … the first person to whom he went was Melanie. Melanie Casto.

And it's not the only allegation Nichols has faced involving a minor. Less than six months after Rhonda's death, he was charged with five counts of sex abuse for allegedly touching a 13-year-old girl on the buttocks. He claims that didn't happen, but something else did.

Peter Van Sant: You sent sexually suggestive texts to her and a selfie with your shirt off. And you agreed to a plea deal in this case –

Stephen Nichols: Yeah, that was [sighs] — that one definitely — I was in the wrong on that one in terms of sending the photo. That was —

Peter Van Sant: No kidding.

Stephen Nichols: Yeah —

Peter Van Sant: That's terrible. That's disgusting.

Stephen Nichols: It is.

Nichols pleaded guilty to one count of sexual harassment.

Stephen Nichols: I have been emotionally abusive at times to people. But I've never physically hurt anyone.

Prosecutors don't agree and want a jury to see a picture taken by Rhonda showing red marks left from an alleged physical encounter with Nichols.

Julia Simmons: Right before they went on their hike … they had a little scuffle on the stairs, and he put some bruises on her back. And she took pictures of them in the mirror.

And there are allegations of another physical assault of a woman with eerie similarities to what Nichols stands accused of now — allegations made by his ex-wife.

Julia Simmons: He did try to push his wife over a balcony in China.

In November 2003, Stephen was still married to his ex, an American woman, and living in China for the first time when his spouse accused him of trying to suffocate her and throw her over the railing of their eighth floor apartment.

Stephen Nichols: We were both holding onto each other's clothing, and we were both yelling.

Nichols denies the claim and was not charged with a crime in China, but Oregon court documents show a witness confirmed Nichols' ex-wife's account.

As Nichols awaits trial in the death of Rhonda Casto, he has some pleasant distraction — visits from his fiancée, Landy.

At "48 Hours"' request, Stephen Nichols has kept a video diary while out on bail,

Stephen Nichols : Today I had my first court appearance. The case was involving my daughter…

The diary includes video of Landy hiking to that fateful spot on Eagle Creek Trail.

Stephen Nichols : We're at the top of Spencer Butte in Eugene. Love the hike, this is one of the happiest days of my life.

And on the eve of his trial, a defiant Nichols is convinced there will be many more happy days ahead.


Stephen Nichols: I had nothing to do with Rhonda Casto's death.

Peter Van Sant: You didn't push her?

Stephen Nichols: No.

Peter Van Sant: So you're telling us you're completely innocent of these charges?

Stephen Nichols: Yes.

In May 2017, following several hearings about what evidence could be used against Stephen Nichols, which would include his plea to having sex with Melanie, it looked like his trueday in court was finally on the horizon.

Julia Simmons: And then I got a call from Carrie Rasmussen, the prosecutor, and she slowly told me the news about him taking a plea.

To Simmons' shock and horror, there had been a settlement conference with the prosecution and the defense agreeing to allow Nichols to plead guilty to lesser charges.

Julia Simmons: I started to cry. I got really upset. …I just said, I was screaming on the phone to Carrie, "No, no, you can't do this. Please don't, don't plead out."

But prosecutors knew their case against Nichols could fail.

Carrie Rasmussen [in court]: For years, the District Attorney's Office has believed that Mr. Nichols is responsible for the death of Rhonda Casto. But this case is not about belief, it's about the facts that can be presented to a jury at trial.

Judge John Wolf: What is your plea to the charge of criminally negligent homicide?

Stephen Nichols: Guilty.

Judge John Wolf: And to the charge of coercion?

Stephen Nichols: Guilty

Mike Arnold: People take pleas for all sorts of reasons. …Most of the time innocent people plead guilty in order to gain an advantage or meet a goal. In this case, this is Mr. Nichols purchasing insurance. There's now zero-percent chance that Steve goes to prison for murder, that a jury gets it wrong.

Nichols was given credit for time served while awaiting trial. He remains on parole for three years. His ankle monitor was removed. And his days behind bars are over.

Peter Van Sant: This plea deal, is it justice to you?

Jessica Colburn: No. It's not justice. …And I felt like it happened out of nowhere. …I'm still completely blown away by the — the decision that was made in this.

Still firmly believing Nichols is a murderer, Rhonda's mother Julia was allowed to address the court.

Julia Simmons: You've destroyed my whole family. Everything, Steve.

Julia Simmons: I don't see how you could do that, how you could take a mother away from her child by killing her. That's just horrible, Steve. …I'll just bide my time and wait until you screw up or when you die, because I know you're gonna go to hell for what you did.

Nichols claims he took the deal for just one reason: time was running out to regain custody of his daughter.

Stephen Nichols: If I waited over a year to go to trial, I probably had a zero-percent chance.

Mike Arnold: There's some problems with the juvenile court system that the longer you wait, the harder it is to get a child returned to parent.

But having now admitted to inappropriate behavior with a 13-year-old girl, pleading to having sex with Rhonda's underage sister and playing a role in Rhonda's death, Nichols' chances of regaining custody of his daughter are in jeopardy.

Stephen Nichols: I think I've just left a path of destruction. I'm Attila the Hun basically, going through women.

Unable to leave Oregon until his parole expires in 2020, Nichols broke up with his fiancée who had returned to China.

Stephen Nichols: I'm alone about 99 percent of the time. …I never go out. …I have nobody.

Then, for the second time in our "48 Hours" interview, Nichols brings up the topic of suicide. But this time, he's not speaking about Rhonda.

Stephen Nichols: If I don't have my daughter, then it's pretty much game over for me. …I'm checking out.

Peter Van Sant: You're saying you'll take your own life.

Stephen Nichols: I hate all the suicide questions. [Laughs] I'm not gonna answer that. But like I said, I — if I don't get my daughter back, I'm done. I'll just say that.

Julia Simmons: Yeah, right. I doubt that. …He's too narcissistic, egotistical, sociopath. …There's no way he would take his own life. …He's just said that to get sympathy.

Peter Van Sant: And if your granddaughter were to be placed back into his custody, what do you think would happen?

Julia Simmons: She would not be a normal child. She would be emotionally and mentally abused, and possibly physical.

And then, just when we thought this story had come to an end, our interview with Nichols took a turn into the surreal.

Stephen Nichols: I'm trying to think of a way to think of this…

For the first time, he talks about what may have happened in Rhonda's last moments of life that day in 2009, comparing her to a wounded soldier.

Stephen Nichols: Let's say you're in a war situation and you're with your buddy, and I don't know, he — he takes a landmine or a grenade or something.

Stephen Nichols: You're 100 percent certain this guy is gonna die.

Remember, Nichols climbed down 150 feet to where Rhonda's broken body lay.

Peter Van Sant: Was she alive when you got to her?

Stephen Nichols: Hmm, now we're — [laughs, then pauses] and that's the part I'm not going into.

Is Stephen Nichols about to admit something?

Peter Van Sant: Did you put Rhonda out of misery that day?

Stephen Nichols: Let me ask you, if you shoot your war buddy because you see how much pain he's in, is that murder?

Peter Van Sant: What do you say?

Stephen Nichols: I say no. Course not. …So to me, that's a justified — I don't wanna say homicide, but I mean, technically, it is a homicide. But it's justified as of that point. You are putting someone out of their misery that essentially has zero chance of survival.

Peter Van Sant: And is that what you did?

Stephen Nichols: That's [laughs] of course that's not what I'm saying. I'm just saying that –

Peter Van Sant: Well, you brought this up.

It seems a dangerous word game. Nichols stood on the cliff's edge, then took a step back. It's a final twist in a tragedy where only Nichols knows the real ending.

Stephen Nichols: It's all hypothetical, because I'm telling people, you know, think — think outside the box. Like there's always other options there.

Since this broadcast last aired, Stephen Nichols publicly admitted to having sex with Rhonda's younger sister, Melanie.

An Oregon court terminated Nichols' parental rights. He is appealing that decision.

casto-model.jpg Casto, Nichols, and daughter web-right.jpg rhonda-casto5.jpg Investigating the death of Rhonda Casto Landy Yin Yan and Stephen Nichols Stephen Nichols booking photo