Colorado Man on Trial for Murder of Girlfriend’s 6-Year-Old Son in 2016 Case
GRAND JUNCTION, COLORADO — A Colorado man accused of killing his girlfriend’s 6-year-old son nearly a decade ago is now standing trial for first-degree and second-degree murder, with prosecutors alleging he strangled the child after losing his temper.
40-year-old Darin Thrailkill was arrested in 2023 for the July 2016 death of Martin Osinski, whose sudden death was ruled a homicide after years of investigation.
Background of the Case
Authorities say the case began on July 2, 2016, when Martin was brought unresponsive to St. Mary’s Hospital in Grand Junction. Despite efforts by medical staff, he was pronounced dead shortly after arrival.
An autopsy later determined the boy had bruising around his neck consistent with strangulation, prompting a yearslong investigation that culminated in Thrailkill’s arrest in North Port, Florida, in October 2023. He was extradited to Mesa County, Colorado, the following month.
Prosecutors argue Thrailkill, who served as a “father figure” to the boy, snapped after the child had a bathroom accident, allegedly choking him to death.
Prosecution and Defense Arguments
In their opening statements, prosecutors said Thrailkill “reached his breaking point” that night and later blamed his 8-year-old son for the incident. They presented evidence of a previous head injury in 2012, which they say shows a pattern of violent behavior.
The defense, however, claims Martin died of medical complications, citing aspiration pneumonia and asthma as contributing factors. They argue Thrailkill discovered the child unresponsive and immediately woke the boy’s mother, Krystal Osinski, who rushed him to the hospital.
“Darin was the easy person to blame,” defense attorneys told jurors. “This case took years because investigators couldn’t prove what didn’t happen.”
Emotional Testimony From the Mother
During Day 4 of the trial, Martin’s mother, Krystal Osinski, testified about her relationship with Thrailkill, describing him as controlling and often harsh in his discipline.
She told the court that on the day of her son’s death, the family had been swimming and spending time outside before she awoke to Thrailkill screaming that something was wrong.
“He was lying flat on his back with no color and no breath,” she said tearfully. “I smelled vomit. I knew he was gone.”
Krystal also told jurors she had previously caught Thrailkill hitting Martin in the face, an incident that was later reported to child services.
Expert Testimony: Medical Findings Disputed
On Day 5, Dr. David Scott, an asthma and allergy specialist, testified that Martin had no evidence of pneumonia or severe asthma during an earlier 2015 medical visit, contradicting the defense’s claim that illness caused the boy’s death.
Dr. Scott stated that the child’s lung function was above average and that there were no medical indicators of respiratory distress leading up to his death.
Meanwhile, forensic pathologist Dr. Dean Havlik maintained that autopsy findings pointed to strangulation, not disease, as the cause of death.
Investigation and Trial Progress
Detective Ed Prescott, who led the 2016 investigation, described how Thrailkill gave conflicting statements and failed to show concern at the hospital.
Officer Patrick Bridge, one of the first responders, recalled finding Thrailkill “intensely nervous and physically shaking” outside the family’s home. He said the suspect did not attempt to go to the hospital or ask about the boy’s condition.
The trial, which began on October 31, 2025, is expected to continue through mid-November. Thrailkill faces life in prison if convicted of first-degree murder.
As the trial unfolds, the case has drawn significant attention in Colorado for its long investigative timeline and emotional testimony from witnesses still grappling with the loss of a child. For continuing updates and courtroom developments, visit ChicagoMusicGuide.com.