Prineville, Ore. – A Crook County Sheriff’s Office deputy has been placed on the District Attorney’s Tier 1 Brady List, the most severe designation under Brady disclosure standards, effectively barring him from being called as a witness in criminal cases prosecuted by the county.
Crook County District Attorney Kari Hathorn confirmed that Deputy Jacob Koski was formally placed on the Tier 1 Brady List on July 17th, 2025, following a months-long Brady inquiry conducted by her office.
According to Hathorn, the Brady inquiry was initiated in May, at which time Koski was notified through his attorney. A meeting between the DA’s office and Koski’s counsel took place a month later, after which additional investigation was conducted before the Tier 1 determination was made. Hathorn stated that as a result of the designation, Koski will not be called as a witness by her office in criminal cases.
“Jacob Koski is on the Brady List – Tier 1. Therefore, he will not be called as a witness by my office,” Hathorn told the Prineville Review.
“On May 9, 2025, I gave notice to Deputy Koski through his attorney, Daniel Thenell, that I was conducting a formal Brady inquiry. Deputy Koski’s attorney requested a meeting to provide additional information for my consideration during the inquiry,” said Hathorn. “That meeting took place June 9, 2025. Subsequently, additional investigation was conducted. On July 17, 2025, I placed Jacob Koski on the Crook County Brady List-Tier 1.”
Hathorn did not cite the specific reasons for Koski’s placement on the Brady List in response to our inquiries.
Koski has worked for nearly six years with the Crook County Sheriff’s Office since graduating from the Oregon Department of Public Safety and Standards & Training in January of 2020, according to the Crook County Sheriff’s Office and state records.
Crook County Sheriff John Gautney confirmed to the Prineville Review that Koski is the subject of an ongoing internal investigation related to an alleged policy violation. Gautney emphasized, however, that the internal investigation is separate from the Brady determination and investigation by the District Attorney’s office on a separate matter.
“There’s been an investigation ongoing prior to the Brady investigation,” Gautney said, adding that the Sheriff’s Office investigation was initiated internally and was not prompted by the DA’s actions.
Gautney also confirmed that no criminal charges have been filed against Koski and that the Sheriff’s Office has not yet reached any disciplinary conclusions.
“There is no criminal part of this,” Gautney said. “The investigation is purely on a potential policy violation within the Sheriff’s Office, and that case is still open.”
The Prineville Review obtained a copy of a February, 2025 tort claim notice through a public records request submitted in October, which shows Koski’s attorney alleged that he was subjected to whistleblower retaliation, claiming adverse employment actions following protected disclosures.
Sheriff Gautney stated that the Brady decision was made independently by the District Attorney’s Office and reiterated that Brady designations are outside the control of his agency.
“The Tier 1 Brady is a designation by the DA’s office,” Gautney said.
Tier 1 Brady designations are generally reserved for the most serious credibility concerns involving law enforcement officers, typically involving findings that directly affect truthfulness or reliability as a witness. Gautney said he was not aware of any prior Tier 1 Brady designations involving deputies within the Crook County Sheriff’s Office during his tenure.
“I don’t know of any in my time that I’ve been here,” he said.
The Sheriff’s Office investigation remains ongoing. No disciplinary action has been announced, and no criminal allegations have been filed. Gautney stated he was unable to provide any further information as the investigation was still ongoing.
Koski’s attorney, Daniel Thenell, did not respond to requests seeking comment earlier this week.
Mr. Alderman is an investigative journalist specializing in government transparency, non-profit accountability, consumer protection, and is a subject matter expert on Oregon’s public records and meetings laws. As a former U.S. Army Military Police Officer, he brings a disciplined investigative approach to his reporting that has frequently exposed ethics violations, financial mismanagement, and transparency failures by public officials and agencies.
