Third District Judge Gabriel McCarthy rejected a defense request for a fixed 25-year term.
CALDWELL, Idaho — Delbert Cornish was sentenced Jan. 28 to life in prison without the possibility of parole for killing his 18-year-old daughter, Hope “Onyx” Cornish, and attempting to kill her 15-year-old brother in an Aug. 18, 2025 attack at the family’s Caldwell home.
The decision followed months of filings and a hearing that drew standing-room attendance. Prosecutors asked for the maximum penalty, arguing the facts and harm merited the harshest sanction under Idaho law. Calling the crime “an act of pure evil,” Judge Gabriel McCarthy agreed. The defense requested a 25-year fixed sentence, citing mental health concerns and asking the court to consider depression and suicidal ideation. The judge said those arguments did not outweigh the record and pronounced a life-without-parole term on the murder count plus additional consecutive time for the other offenses.
Chief Deputy Prosecutor Ingrid Batey told the court Cornish’s actions were “senseless, cruel, cowardly, and callous.” Deputy Prosecutor Stephanie Morse assisted for the state. Prosecutor Chris Boyd thanked Caldwell Police, Canyon County Sheriff’s deputies and the Coroner’s Office for their work, saying the ruling ensures the defendant “wakes up behind bars every day for the rest of his life.” The case also included an animal-cruelty count tied to the shooting of the teen’s pet cat. The victim’s younger brother survived the attempted killing; officials did not release medical details, and the teen was not present in court.
The timeline presented in court dates the killing to the evening of Aug. 18, 2025, in a residential Caldwell neighborhood. Detectives processed the home, recovered evidence and conducted interviews. In subsequent hearings, the court accepted filings that set up the Jan. 28 sentencing. Idaho does not require a jury to set punishment in this type of case; the judge imposed life without parole after considering statements and the presentence investigation. The clerk recorded the judgment the same day, and deputies took Cornish into custody for state prison intake.
On the courthouse steps, quiet conversations mixed with the sound of traffic along Albany Street. A small group left flowers near a low wall by the entrance. “We want people to remember her for her life, not for her death,” the teen’s mother said after the hearing. A neighbor from the block where the crime occurred said the case “left everyone on edge for months” and that the sentence “felt like finality.” Others declined to speak, nodding as they walked to their cars.
As of Friday, no additional hearings were scheduled. The life-without-parole term means the defendant is not eligible for release. Any appeal would proceed under normal Idaho deadlines and be publicly recorded in the docket.
Author note: Last updated February 1, 2026.