When Rhonda Casto set out on March 16, 2009, for a hike with her boyfriend, her family had no idea the day would transform into a nightmare — one that ended with Casto’s lifeless body at the bottom of a steep ravine.
The plan was for Casto, a 23-year-old aspiring model, to walk the popular Eagle Creek Trail along Oregon’s Columbia River Gorge accompanied by her boyfriend, Steve Nichols.
Casto handed their 9-month-old, Ava, to her mother that morning and she and Nichols headed off.
“She was so happy,” Nichols tells PEOPLE. “It was a nice day starting out.”
By nightfall, Casto was dead.
Though Nichols says he doesn’t remember much about what happened, he does recall Casto running along the narrow trail with a towel over her shoulders, like “Superwoman,” and he says he witnessed her fall. He tried to help her, he says — sliding down the ravine and trying to swim across a freezing creek to get to her.
However, by the time he reached her body, he says, he collapsed on top of her from exhaustion and hypothermia.
“I fell asleep on her chest and I don’t know how long I was asleep for, but I woke up and I realized I was shaking uncontrollably because I was so cold,” he says. “I had hypothermia. I made my way back to the car and called 911.”
Nichols says he believes prescription drugs played a part in Casto’s death, which he called an accident, and he claims he later discovered she was using marijuana and also taking medication to lose weight and for depression.
But Casto’s mother, Julia Simmons, doesn’t buy Nichols’ story and believes her daughter would never put herself at risk.
“She would never skip down a trail that narrow,” she says. “She had a baby at home that needed her.”
Within days of Casto’s death, investigators, too, began to question Nichols’ account of her fatal fall.
• For more on Casto’s sudden death and the investigation that followed, subscribe now to PEOPLE or pick this weeks issue, on newsstands Friday.
In February 2015, nearly six years later, Nichols was arrested and charged with killing Casto — accused of pushing her off a 100-foot cliff so he could collect a $1-million life insurance policy.
Authorities also pointed to an alleged inappropriate relationship with Casto’s underage sister and a previous incident where Nichols was accused of attempting to push his then-wife off a balcony in China in 2003. Nichols has denied all of these claims.
And then in May, in a move that angered Casto’s family, prosecutors dropped the murder charge against Nichols. In return, he pleaded guilty to criminally negligent homicide and coercion.
The case, already years in the making at the time of Nichols’ arrest in 2015, had encountered multiple legal obstacles as his prosecution proceeded.
According to his plea, Nichols received three years’ of probation, with credit for 19 months of jail time.
“It is like a slap in the face for me and a slap on the hand for him,” Simmons says. (The Hood River County, Oregon, District Attorney’s Office, which brought the charges against Nichols, declined to comment.)
Casto’s family says they aren’t sure her death was accidental, as Nichols has insisted. Her friends described her relationship with Nichols as volatile, and her mother says she was considering ending things with him before she died.
‘The Relationship Wasn’t a Good One’
Casto was a 20-year-old Texas transplant when, in 2005, she met Nichols through her mother, who was renting a room in his three-bedroom condo.
Nichols, then a 30-year-old day trader in Portland, Oregon, soon began tutoring Casto, who was taking college courses, and their relationship escalated.
“She told me he spoiled her,” says Casto’s friend Jen Sconce. “Money-wise he treated her like a princess.”
But, Sconce says, the relationship was “tumultuous.”
“I think she knew the relationship wasn’t a good one,” Sconce says.
In the months before Casto’s death, Simmons — who pleaded guilty in July to embezzling Social Security survivor benefits intended for her granddaughter — says she was thinking of leaving Nichols.
“She would complain how he treated her and how they weren’t getting along,” Simmons says. “She was going to move out, but she was trying to get up the courage to do it. She was worried about not having enough money to support Ava.”
Nichols denies he was having any relationship problems with Casto. “We hardly ever fought,” he says. “I am not a fighter. I don’t really get angry.”
In 2014, Nichols, who was teaching in China and living with Ava, was charged with Casto’s murder by secret indictment. He was arrested in February 2015 at the San Francisco International Airport, when he returned to the country.
However, in February of this year, the prosecution’s case against Nichols suffered a major setback.
The Oregon Supreme Court ruled a three-hour police interview with him after his arrest was inadmissible. Adding to the prosecution’s problems was the fact that the former lead detective, who had retired in 2012, destroyed evidence on his computer, including crime scene and autopsy photos and trail-head fee envelopes from potential witnesses.
• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.
For his part, Nichols, now 42, continues to say he had nothing to do with Casto’s death.
He says she was high on drugs and slipped off the edge of the cliff: “When we started hiking up the trail, I knew something was wrong with her.”
For Simmons, the years since Casto’s death have been difficult — and moving on has been even harder. She says she has leaned on her faith that one day she will be reunited with her daughter, who she says is watching over her and Ava.
“She is in a good place and not hurting or unhappy,” Simmons says of Casto. “I want to one day see her again. I look forward to that day.”