A former Bend-area man accused of pushing his girlfriend off a cliff along the Eagle Creek trail in the Columbia Gorge pleaded guilty this week to criminally negligent homicide and coercion, concluding an 8‑year‑old case marked by arguments over a $1 million insurance policy, a secret indictment and a bungled investigation.

State prosecutors dropped a murder charge against Steven P. Nichols this week in a plea deal.

Nichols, 42, was placed on three years probation with credit for the year and seven months he already served in jail awaiting trial.

Rhonda Casto, 23, of Portland, the mother of the couple’s then‑infant daughter, died when she fell during a hike with Nichols on March 16, 2009.

Nichols’ lawyer, Mike Arnold, had aggressively challenged the murder case, successfully pointing out flaws — from the destruction of evidence by an investigator to an unconstitutional three‑hour police interview of Nichols after Nichols was arrested on a warrant in 2015.

The initial lead detective destroyed evidence on his computer, including crime scene and autopsy photos and trailhead fee envelopes from potential witnesses before he retired, court records indicated.

A Hood River County judge later suppressed Nichols’ statements to San Mateo County sheriff’s detectives in California who arrested Nichols at San Francisco International Airport in 2015. When asked about his girlfriend’s death, Nichols had said under the questioning that “it’s not something I want to talk about,’’ but detectives continued to ask him questions for about three hours.

The state appealed, and the Oregon Supreme Court two months ago upheld the suppression of Nichols’ statements, finding the police interview should have ended once he protested.

“We concluded that the defendant unequivocally expressed an intent to invoke his right against self‑compelled incrimination, which a reasonable officer would have understood as an invocation of that right,’’ the Supreme Court ruling said.

Casto fell 100 feet to her death about a mile from the trailhead along a narrow section featuring wire cables and pipe handrails for safety. Nichols was a suspect in the death from the beginning.

He called 911 at 6:09 p.m. to report that Casto had slipped as they were hiking. He said it took him an hour to scramble down to her body and that he began “mouth to mouth” resuscitation, then lay on top of her for 45 minutes until he got cold. He didn’t explain why.

Several months before her death, Nichols had increased Casto’s life insurance policy to $1 million, records show. He had tried to collect it after her death and eventually agreed to split it with Casto’s mother and with the estate of the child he had with Casto.

Casto’s mother, Julia Simmons, now faces a federal charge herself, accused of embezzling Social Security funds that she wasn’t entitled to, according to court documents.

As an investigation into the death proceeded, Nichols continued to live in the Bend area for several years before he traveled to China for about a year and a half with his daughter. In 2014, Hood River County prosecutors obtained a secret indictment against Nichols as he was still in China. He was arrested when he returned to the country at the San Francisco airport.

The dismissal of the murder charge and guilty pleas to two other felony charges followed settlement negotiations between Hood River County Deputy District Attorney Carrie Rasmussen and Arnold.