Thrailkill Found Guilty of First-Degree Murder in 2016 Death of 6-Year-Old Martin Osinski

GRAND JUNCTION, Colo. — Nearly ten years after the death of six-year-old Martin Osinski, a Mesa County jury on Monday found 40-year-old Darin Thrailkill guilty of first-degree murder. The verdict concludes a long, complex investigation into a case prosecutors described as one of the most difficult of their careers.

Martin was brought to St. Mary’s Medical Center in July 2016 already cold to the touch and showing no signs of life. Doctors quickly noted suspicious bruising, marks around his neck, and severe petechiae—burst capillaries visible around his eyes and ears. An autopsy later ruled the cause of death as homicide by asphyxia consistent with strangulation.

Five people, including Martin’s mother, Krystal Osinski, and Thrailkill—her then-partner—were inside the home that night. Witnesses reported hearing screams before Martin was discovered unresponsive. Police also found children’s underwear with apparent fecal matter, something prosecutors said routinely triggered Thrailkill’s anger.

During trial, one of Thrailkill’s sons, who was eight years old at the time, testified that Martin had soiled himself that night and that Thrailkill became angry. He told jurors he heard Martin scream. Prosecutors argued that this incident led to Thrailkill strangling the boy.

Conflicting Claims on Cause of Death

The defense attempted to cast doubt on the cause of death, arguing that Martin had a history of illness and pointing to the 2016 autopsy’s note that his lungs were enlarged, suggesting possible interstitial pneumonia. But two medical experts testified that Martin showed no signs of pneumonia and instead exhibited a “constellation of injuries,” including extensive bruising and clear trauma consistent with strangulation.

Prosecutors showed the jury photos during rebuttal: one of Martin smiling

^{Darin Thrailkill 2023 Inmate Photo}   

with a snow cone, and another of him lifeless on a hospital gurney. “You go from a happy little boy to a dead little boy in 30 seconds,” one prosecutor told the court.

A Case Complicated by Years of Delays and Disturbing Events

Thrailkill had been investigated for previous incidents involving Martin, including a skull fracture in 2012. After Martin’s death, the case became mired in delays and unusual developments. At one point, Thrailkill sent messages to his father implying his own eight-year-old child was responsible for Martin’s death. In 2017, he was taken to the hospital following a suicide attempt and later tested positive for meth. Only days after that test, he left Colorado for Florida.

A formal arrest was not made until 2023. Thrailkill was extradited back to Mesa County in October of that year to face trial on charges of first-degree murder for knowingly causing the 

death of a child under 12 while in a position of trust, as well as an additional count of first-degree murder for knowingly causing the death of another person.

District Attorney Dan Rubinstein emphasized how challenging the case was to try. “It was about a six-year-old case when we arrested him,” Rubinstein said, noting Thrailkill’s arrest in Florida and lengthy extradition process. He also credited retired prosecutor Trish Mayer, who returned specifically to assist with the trial.

Rubinstein praised the jury for its diligence. “We need 12 jurors to unanimously find the defendant guilty beyond a reasonable doubt,” he said. “That’s always a difficult burden because our system is designed to ensure no innocent person is ever found guilty. But we were successful in proving this case.”

Sentencing Set for Tuesday

Thrailkill now faces life in prison without the possibility of parole—the mandatory sentence for first-degree murder in Colorado. Sentencing is scheduled for Tuesday at 1 p.m. The court delayed the hearing so Martin’s mother and other loved ones could prepare their statements.

“It’s only one possible sentence,” Rubinstein said, “but it’s important that the family has the chance to speak.”

Judge Upholds Life Sentence for Thrailkill Despite Defense Objections

At a sentencing hearing on Tuesday, defense attorneys for Darin Thrailkill argued that a mandatory life sentence without the possibility of parole constituted cruel and unusual punishment. Their objection followed Thrailkill’s conviction for the 2016 murder of six-year-old Martin Osinski.

District Judge Brian Flynn rejected the defense’s argument, stating the sentence was both lawful and appropriate given the severity of the crime.
“I’ll just say that I don’t find it to be cruel and unusual punishment when someone is convicted of killing a child in a very violent way,” Judge Flynn said.

Emotions ran high throughout the hearing. Martin Osinski’s father, who testified during the trial, addressed the court and directed a brief but powerful statement toward Thrailkill.
“I just want him to know that I hate him for ruining my life and the trauma that I deal with every day," he said.

Several members of Thrailkill’s family also spoke, offering statements of support and expressing hope for healing. Thrailkill’s mother, Natalie Freeman, read a message on behalf of two of his brothers: “When one door closes, despite everything that’s going on, another will open.”

When given the opportunity to speak, Thrailkill addressed his family directly.
“I just want to say to my family, thank you, I love you, and I hope to see you guys,” he said. He encouraged his children to write to him and said he planned to write back. “It’ll get a little better,” he added.

Thrailkill will serve a life sentence without the possibility of parole.