GRAND JUNCTION, Colo. (Court TV) — A Colorado man is standing trial for allegedly murdering his girlfriend’s 6-year-old son.
Darin Thrailkill, 40, was arrested in 2023 for the July 2016 death of Martin Osinski. He’s charged with first-degree murder and second-degree murder.
FILE – This 2023 booking photo provided by Grand Junction Police Department shows Darin Thrailkill. (Grand Junction Police Department)
An investigation began when the unresponsive boy was brought to St. Mary’s Hospital on July 2, 2016. Despite life-saving efforts, Osinski was declared deceased. An autopsy later ruled the manner of death a homicide.
The case remained under investigation for more than seven years before authorities obtained an arrest warrant for Thrailkill in October 2023, according to Grand Junction Police. Thrailkill was located and arrested in North Port, Florida, on October 3, 2023. He was subsequently extradited back to Mesa County that November.
In opening statements, prosecutors argued that Thrailkill had “reached his breaking point” after Martin, who wore pull-ups, had a bathroom accident. Thrailkill’s defense claims the boy died from a combination of aspiration pneumonia and asthma.
Mother describes finding her son unresponsive
Martin’s mother, Krystal Osinski, testified about the night her son died. She had been in a relationship with Thrailkill from 2012 to 2016, during which he served as a father figure to Martin.
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Krystal described the chaotic scene when Thrailkill woke her up around 10:30 p.m., telling her something was wrong with Martin. She found her son unresponsive in his bedroom and immediately drove him to the hospital, where medical staff attempted resuscitation for more than 20 minutes before declaring him dead at 11:20 p.m.
“I knew something was wrong. I knew something was off,” Krystal testified about discovering Martin’s body.
Officer describes defendant’s behavior
Officer Patrick Bridge, who responded to the home after Martin was taken to the hospital, described Thrailkill as “intensely nervous” and “physically shaking” when he found him sitting on the front porch.
A photo of Martin Osinski is shown in court during the murder trial of Darin Thrailkill on Nov. 4, 2025. (Court TV)
Thrailkill told Officer Bridge he checked on the children nightly and found Martin not breathing with a pillow over his head. Bridge noted that Thrailkill didn’t ask about Martin’s condition, didn’t express emotion, and didn’t ask to go to the hospital.
Medical examiner maintains strangulation finding
Dr. Dean Havlik, the medical examiner who performed Martin’s autopsy, testified that the boy died from strangulation and noted bruising on his neck. Despite defense challenges about Martin’s history of asthma and respiratory issues, Dr. Havlik maintained his opinion that the child was strangled to death.
The defense presented medical records showing Martin had been treated for asthma-related symptoms from 2013 to 2016, including prescriptions for medications like albuterol. However, Dr. David Scott, an allergy and asthma specialist who examined Martin in 2015, disputed any possibility that the boy had pneumonia during his visit.
Scott testified that Martin’s lung function test results were in the 96th percentile, which he described as excellent for a 5-year-old, and that comprehensive allergy testing was negative.
Witnesses in this trial should not watch any proceedings until released from subpoena.
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