“Poison Twist”: Dateline Reports on Mary Yoder Homicide March 21 2025

This Friday, March 21, 2025, at 9/8c, Dateline NBC airs “Poison Twist,” an in-depth investigation into the poisoning death of Mary Yoder and the conviction of Kaitlyn Conley. The episode delves into the complex case that began as a medical mystery and evolved into a legal battle over guilt, motive, and justice. With exclusive interviews, new evidence, and insights from those closest to the case, Dateline explores the twists and turns that led to Conley’s manslaughter conviction—and her continued fight to overturn it.

A Sudden and Suspicious Death

Mary Yoder, a 60-year-old chiropractor from Whitesboro, New York, was a beloved member of her community. She ran a successful chiropractic practice with her husband, Bill Yoder, where they worked alongside their son, Adam, and Kaitlyn Conley, Adam’s former girlfriend.

On July 20, 2015, Mary fell violently ill with symptoms that initially appeared to be a severe stomach virus. She was admitted to the hospital, but her condition deteriorated rapidly. Less than 48 hours later, she died. Her sudden death left doctors and loved ones searching for answers. It was not until weeks later, when a toxicology report was completed, that authorities discovered the cause—colchicine poisoning.

Colchicine, a medication used to treat gout, can be lethal in high doses. It was not something Mary had ever been prescribed or would have taken voluntarily. Investigators now had a homicide case on their hands.

The Investigation Begins

Law enforcement initially focused on those closest to Mary, including her husband Bill and son Adam. Both had access to her workplace and personal space, and both had their own struggles following her death. Bill had begun dating Mary’s sister, which some found suspicious. Adam had a history of personal and emotional conflicts with Conley, which became a critical point in the investigation.

The case took a sharp turn when police received an anonymous letter that suggested Adam should be investigated. The letter specifically mentioned that he had colchicine in his car. When police searched Adam’s vehicle, they found a bottle of the deadly drug under his seat. This discovery briefly shifted suspicion onto him. However, when investigators traced the letter back to its source, they found that it had been written by Kaitlyn Conley.

Suspicion Falls on Conley

Conley had worked as the office manager at the Yoder family’s chiropractic clinic. She had been in an on-and-off relationship with Adam, described by those close to them as volatile. Conley had accused Adam of abuse, but law enforcement found no evidence to support her claims.

When police interviewed Conley, her statements raised red flags. She repeatedly pointed to Adam as a suspect and insisted he had acted strangely after Mary’s death. Investigators noticed inconsistencies in her story, and when pressed about the method of poisoning, she made a comment that stood out: “Men don’t use poison. That’s a lady’s weapon.” This remark, coupled with her behavior, deepened police suspicion.

Forensic analysis of Conley’s work computer revealed that someone had ordered colchicine online using the clinic’s computer. The purchase was linked to Conley’s email account. This, combined with her attempt to frame Adam, placed her at the center of the investigation.

The Trial and Conviction

In 2016, Conley was charged with second-degree murder. The first trial ended in a hung jury, unable to reach a unanimous decision. The prosecution argued that Conley had poisoned Mary out of revenge against Adam, seeking to inflict suffering on him and his family.

During the second trial in 2017, the jury found her guilty of first-degree manslaughter. The conviction carried a 23-year prison sentence. Prosecutors acknowledged that while they could not definitively prove premeditated murder, the evidence showed that Conley had deliberately administered a fatal dose of colchicine to Mary.

Conley and her defense team maintained her innocence. They argued that there was no direct evidence placing the poison in Mary’s body and that Conley was being scapegoated due to her troubled relationship with Adam.

A Family Divided

The verdict left a permanent divide between the Yoder and Conley families. Mary’s husband and children firmly believe that Conley is guilty, calling her manipulative and dangerous. Adam’s sister, Tamaryn Yoder, expressed her anger, saying she hopes Conley never walks free.

On the other side, some of Mary’s own relatives, including her sisters, supported Conley and launched a campaign to overturn her conviction. They believe the case was mishandled and that Conley’s conviction was based on circumstantial evidence rather than undeniable proof.

Conley’s parents continue to advocate for her release, asserting that she did not receive a fair trial. Despite their efforts, multiple appeals have been denied.

The Ongoing Fight for Freedom

Now incarcerated at Bedford Hills Correctional Facility, Conley has not wavered in her claims of innocence. She has stated that she was unfairly targeted and that investigators ignored other potential suspects.

Her legal team is preparing another appeal, arguing that key evidence was misinterpreted and that new forensic analysis could challenge the prosecution’s timeline. However, with each failed appeal, the likelihood of her serving her full sentence increases.

The Case That Won’t Be Forgotten

Dateline NBC’s “Poison Twist” revisits the complex web of relationships, betrayals, and forensic evidence that led to Kaitlyn Conley’s conviction. With interviews from both sides of the case, the episode sheds light on the unanswered questions that still haunt those involved.

The case remains one of the most debated poisonings in recent history, leaving lingering doubts, unwavering convictions, and a family forever divided.