In New York, a beloved chiropractor dies suddenly. When her autopsy reveals she overdosed on a prescription she didn't take, police believe they have a murder on their hands.

New York chiropractor Mary Yoder, 60, attended to her patients at her Whitesboro Medical Practice, a successful chiropractic business she and her husband Bill have owned for more than 30 years.

Yoder became ill one Sunday after seeing patients throughout the day. Not able to shake her sickness, Yoder went home early around 4:30 p.m.

"She doesn't know what she's sick from, she's just having diarrhea and vomiting at this time," said Oneida County Sheriff's Lieutenant Robert Nelson.

Mary Yoder is usually the picture of health. Part of her medical practice included a belief in holistic medicine and herbal supplements, even growing some of her own herbs in her cherished home garden.

Back at her home, Yoder decides to try and sleep it off. But by morning her symptoms have taken a turn for the worse.

"The following morning her husband, Bill, brings her to the St. Luke's emergency room," said Nelson.

Yoder is admitted to the hospital and doctors run a battery of tests trying to identify what's making her so violently ill. It's now been over 24 hours since she first became sick.

"At 10 p.m. she gets up and she falls in the room at the hospital and after that, they admit her into I.C.U. at the hospital, where she just continues to deteriorate," said Nelson.

By morning, Yoder suffers her first heart attack, followed by seven more.

"Then the final one in the afternoon is when she passes away," said Nelson.

Just 48 hours after leaving her office, on July 22, 2015, Yoder is dead. Cause of death? Doctors are at a loss. Since Yoder dies under the hospital's care, a routine autopsy is ordered.

"They look at the slides underneath the microscope -- there's something not right," said Nelson.

Yoder's tissues and organs show they are under attack. It's a telltale sign of poison.

The medical examiner's office contacts Poison Control for help. They test Mary Yoder's body for common arsenic and cyanide poisons. The results are negative. Two months pass, and chemists at Poison Control get a positive hit.

"She died from colchicine, a toxicity which poisoned her," said Utica Observer-Dispatch crime reporter Micaela Parker.

Colchicine, when used properly, is an effective medicine for treating gout, is an inflammation of the joints.

But if you don't have gout?

"A little dab will do it," said Lt. Nelson. "It takes only a minute amount to get somebody sick or kill them."

"Colchicine toxicity causes fever, abdominal cramping, vomiting -- basically all of your liquids leave your body," said Parker.

Now that they know the substance that killed her, investigators have to find out how it got in her body.

"She has a garden and she had taken something from the garden, and she also takes supplements, so they were also looking at the supplements to see if there was any contamination with supplements they had collected and sent out for tests," said Nelson.

The results: No contamination. It was no accident. And suicide is ruled out after investigators speak with friends and family.

That leaves just one unsettling option: "Somebody murdered her," said Nelson.

Mary Yoder's death is ruled a homicide by the medical examiner's office. But who poisoned her?

"Anytime anyone dies, the spouse is somebody that's looked at, usually very hard, and for good reason. Oftentimes they're responsible for it," said Oneida County District Attorney Scott McNamara.

On the day Yoder became ill, her ever-present husband, Bill, was absent from the office. According to the Oneida County Sheriff's Department, they didn't have much more information about Bill's whereabouts that day, other than he wasn't at work.

Not long after Mary Yoder died, he reportedly started dating her sister.

"At this point we're still looking at Bill as our primary suspect if he is responsible," said Lt. Nelson.

Then authorities receive anonymous letters.

"The Onondaga medical examiner's office calls the sheriff's department, they've received an anonymous letter that claims to have information regarding the case," said reporter Micaela Parker. "That same day, the Oneida County Sheriff's Office receives an identical copy of that letter claiming the same."

The letters claimed to know who poisoned Mary Yoder.

"They pointed to Mary Louise Yoder's youngest child, Adam Yoder," said Parker.

And the letters identify the lethal lacing by name: colchicine.

Cops rule out Bill Yoder and turn their focus on the son. Adam is quickly brought in for questioning, and he's grilled about the letters.

"We tell him some stuff that's in the letter, it's saying there was some evidence in Adam's car that we would be interested in," said Lt. Nelson.

Sheriff's deputies inspect the car and just as it was described in the letter, under the passenger's seat, they find it.

"A bottle of colchicine, a cardboard wrapper, and receipt detailing the transaction, and that receipt has an email address that is similar to several that Mr. Yoder has," said Parker.

Cops appear to have their prime suspect. Now they just need to corroborate their findings and interview potential witnesses. They start with those who know Adam best, like his on-and-off girlfriend, Kaitlyn Conley.

"When Mary Yoder died, Katie was identified as a loved one in her obituary," said Parker.

Conley also worked for the Yoders at their chiropractic business.

"She works the front desk, she's borderline receptionist, office manager, she's been working there for four years," said Parker.

Conley was very close with Yoder and her family and even wrote a Facebook post the day after Yoder died. She wrote "If love could have saved you, you would have lived forever," and ends with the thought, "God has gained the best angel. We love you."

Detectives figure if anything suspicious was going on between Adam and his mother, Conley might know about it.

"We were hoping she would be a witness and provide us information about Dr. Yoder," said Lt. Nelson. "She's pointing the finger at Adam."

While investigators bring in Conley for another interview, explosive details come back from the state police forensics lab: They believe the letters originated from the Yoders' place of business, and they've tested the anonymous letters for DNA.

"They said there was female DNA underneath the stamp," said Nelson.

Investigators ask Conley for a DNA sample, and she readily offers it up.

"She describes to us what she does in the office, as far as she pre-stamps the envelopes," said Lt. Nelson.

Kaitlyn Conley even reportedly brings in envelope samples and letterhead from the office.

At this same time detectives take another look at the evidence collected from Adam's car. Along with the poison was the receipt and an email address attached to the transaction.

"When he's questioned about this, Adam says it's similar to some that I have but that's not my account," said Parker.

The email address has only been accessed in two places: at Kaitlyn Conley's home and on her cellphone.

Investigators are starting to believe that Adam Yoder was being framed, and that the evidence in his car was planted. As detectives enter into their fourth and final interview with Conley, she continues to point the finger at her ex-boyfriend, Adam. And to detectives, her story sounds oddly familiar.

"We had always believed that whoever wrote this letter is responsible for Mary's death," said Lt. Nelson.

So detectives ask her flat out if she wrote the anonymous letter.

"At which time she admitted that she was the author of the letter, she wrote the letter," said Lt. Nelson.

Kaitlyn Conley is no longer a witness.

"From that point on she was a number one suspect for us," said Nelson.

Kaitlyn Conley, 23, is arrested charged with second-degree murder in the death of Mary Yoder. But cops still don't have a motive.

The Oneida County courthouse is packed as opening statements begin in the sensational murder trial that rocked the quiet upstate New York city of Utica.

"I'm telling you right here and now that this case is entirely about motive," Kaitlyn Conley's defense attorney Christopher Pelli said in court.

Pelli claims only one person had the motive and means to kill Mary Yoder.

"The decedent's husband. It's hard to swallow, but it's there," said Pelli.

Bill Yoder, the same man who cops began looking at after he went suspiciously absent from their business on the day Mary Yoder became ill.

The defense claims Bill likely laced Mary's daily protein shake that morning before work, and that's why he avoided the office that day.

"Bill is brilliant, he is a two-time Ph.D., he's a highly intelligent man. And he's a detailist. He has motive," said Mary Yoder's sister Janine King.

Motive, according to the defense, in the form of an alleged illicit affair with Mary's older sister, Kathleen Richmond.

"We found out that there were several witnesses that placed Kathy and Bill together prior to Mary's passing, including her neighbor," said Sharon Mills.

And there's something else the defense claims directly connects Bill to the toxin that killed his wife.

"'Super Weed,' as the defense called it. Killer weed," said journalist and radio personality Rocco LaDuca. "During the '80s, it was acknowledged that there was a mixture that was used, he said Mary came up with this mixture that was used to enhance the growth of plants. Exactly what colchicine would do if it was used to grow marijuana. All you have to do is go on the internet and look that up."

In fact, the defense claims Mary likely ordered this drug, never knowing that it would one day be used to kill her.

But prosecutor Laurie Lisi claims Bill Yoder had nothing to do with it. She says it was all Kaitlyn and the motive for murder is pure and simple: revenge.

Basically, that after Adam Yoder broke up with the defendant:

"Kaityln was a woman scorned. She wanted to try and get back at Adam by killing his mother," said Rocco LaDuca.

But two of Mary's own sisters adamantly disagree with the prosecution.

"We thought she was being framed," said Janine King.

Do you believe Kaitlyn Conley is responsible for your sister's death?

"No. Not at all," said Mary's sister Sharon Mills.

And after three weeks of testimony and five days of deliberations, the defense was able to create enough reasonable doubt to leave jurors hopelessly deadlocked. The judge was forced to declare a mistrial.

But prosecutors don't let the charges drop, and five months later Kaitlyn Conley is back on trial for murder.

Then a huge gamble. Right before the start of Kaitlyn's second trial, her family hires a new attorney.

"Mary Yoder died from colchicine poisoning. That's true. And that's the only thing that will be proven in this case," defense attorney Frank Policelli said in court.

And what's more, a bold and risky move by Kaitlyn's defense team when they completely change their defense strategy. This time, her new attorney, Frank Policelli, plans to abandon the theory that Mary's husband did it, and instead he points the finger squarely at Mary's son and Kaitlyn's ex-boyfriend, Adam Yoder.

"Adam is a troubled person and Mary and he had had a falling out," said Janine King.

The defense begins with painting a toxic relationship between Kaitlyn and Adam built on co-dependence, and even violence. Mary's nephew, who lived with Adam around the time he dated Kaitlyn Conley, took the stand to testify to their tumultuous relationship.

You think Katie was a victim of domestic violence at the hands of Adam, allegedly?

"I do," said David King, Mary Yoder's nephew.

Also, the defense claimed Adam, not Kaitlyn, was the one full of revenge, and that he set out to frame her for his mother's murder after Kaitlyn refused to get back together with him. The defense even enters into evidence text messages from Adam to Kaitlyn where he appears to be begging her to come back.

In one text Adam writes: "I miss you a lot. I'm thinking about you always."

Then in another text, when Kaitlyn claims she got pregnant with Adam's baby and terminated the pregnancy, Adam responds: "I'm so [----] torn up and hurt and confused now."

Katie writes: "I didn't want to do that alone and you didn't want to be there."

Adam texts back: "You wouldn't have been [----] alone, I'm not a piece of [----]. That decision should have been made by 2 people either way."

"He said he intended to marry her at one point," said David King.

These texts from Adam Yoder appear to undermine the prosecution's case that Kaitlyn Conley killed Mary Yoder in retaliation after Adam rejected her. Still, the prosecution never wavers from their main theory.

"That she was trying to get back at Adam," said Rocco LaDuca.

But there is one significant thing that prosecutors do change from the last trial to this one. Prosecutors added on the lesser charge of first-degree manslaughter for the jury to consider if they find Kaitlyn not guilty on the second-degree murder charge.

Then after weeks of testimony, jurors begin deliberations. And they request to take another look at a moment captured on police interrogation video where an investigator asks Kaitlyn why she believes Adam would keep the poison in his car that would directly link him to the crime.

"I think he would keep it if he wanted to use it for someone else," Kaitlyn says in the recorded interrogation. "Right, but guys also don't use poison."

"A lot of them do," the detective says.

"They say it's a lady's weapon," Kaitlyn says.

Jurors wonder if it's a curious statement, or a guilty slip of the tongue. Either way, they don't seem to be buying the new defense that Adam Yoder is the real killer. Instead, they appear to side with the prosecution's presentation of electronic evidence against Kaitlyn, including incriminating searches and transactions captured on the defendant's cellphone and computer.

"The cellphones, the computers and all those things that were forensically examined, those are what the prosecution really relies on and says that realistically, reasonably, who else would have been using these devices to look up the poison, to create the letter of intent?" said LaDuca.

"The evidence is clear and that the common denominator is this defendant, Kaitlyn Conley."

The now 24-year-old Kaitlyn Conley is found guilty of first-degree manslaughter. But before sentencing, Kaitlyn's defense attorney makes a final plea for the verdict to be thrown out, claiming prosecutors did not prove their case beyond a reasonable doubt that Kaitlyn poisoned Mary.

"You cannot prove that on July 20th, 1:15 in the afternoon at the business of the chiropractic, Kaitlyn Conley poisoned Mary Yoder. It's not there, it never will be there, and the jury's verdict was irrational, and you should set aside the verdict. Thank you."

Then it's time for victim-impact statements. Mary Yoder's son and Kaityln's ex-boyfriend Adam Yoder has a few choice words for his former flame.

"I introduced Katie Conley to my family, and because I loved her, they all accepted her and treated her as family, as blood. Make no mistake, I hate the defendant with every bone in my body and every drop of blood in my veins. I hate Kaitlyn Ann Conley because Kaitlyn Ann Conley murdered my mother."

And Mary's husband of 40 years, Bill Yoder, also addresses the court.

"To get even with my son, she decided to murder his mother."

And then you could hear a pin drop as Kaitlyn makes her way to the podium for a final statement to the court before learning her ultimate fate.

"With all due respect to the justice system and to our jury system, I am innocent. And I would like to thank my family and friends and strangers that are standing up in support of me."

Support, yes, and you'll never believe who is in Kaitlyn's corner.

"Dear Judge Dwyer, Mary Yoder was my sister. I am writing to you to plead for mercy and leniency as you decide on Kaitlyn's sentence," said Janine King in court.

It's the moment everyone has been waiting for as Judge Michael Dwyer announces Kaitlyn Conley's fate.

"The evidence presented at the trial indicates that Ms. Conley was the only person at that time that knew why this was happening and how her life was going to end. It will be the sentence of this court as to the defendant's conviction for manslaughter in the first degree that she will be sentenced to a 23-year determinant sentence in state prison."

After two trials and weeks of testimony, this bizarre case comes to a close -- but not for everyone involved, including some of Mary Yoder's family members, and making frequent appearances on crime reporter Rocco LaDuca's talk radio show.

"I spoke with several sisters of Mary Yoder," LaDuca tells Crime Watch Daily. "They believe Kaitlyn in this case, the wrong person is being punished for this. That troubles them because they know Kaitlyn as well, and they certainly know what Mary thought of Kaitlyn, and they can't believe that she did this."

And LaDuca is quick to point out that there wouldn't have been a murder investigation if it wasn't for these same sisters speaking out.

"It wasn't Mary's husband or son or daughters that alerted the sheriff's office. It was the same sisters of Mary who alerted the sheriff's office who now are saying they believe they've arrested the wrong person," said LaDuca.

So if not Kaitlyn Conley, who do they believe really killed Mary Yoder?

"My brother-in-law and my nephew are responsible for my sister's death," said Janine King.

Her allegation goes against all the evidence presented to the jury. In addition, neither Bill or Adam Yoder has ever been charged in Mary's death, and they have always maintained their innocence. But despite this, a few of Mary's family members still question Kaitlyn Conley's conviction.

"I believe that a young woman has been wrongfully convicted and that the persons involved in my sister's death have immunity," said King.

Mary's sister Janine King claims that prosecutors made their first mistake by granting full immunity to both Bill and Adam in exchange for their testimony for Kaitlyn's grand jury proceeding.

"It's blanket immunity, total immunity. It can never be revoked," said King.

But the prosecutor defends his decision.

Were they given blanket immunity?

"OK, so in New York state, it's transactional immunity. However -- and this is the part that always somehow or another gets left out -- however, you do not get immunity if you lie," said Oneida County District Attorney Scott McNamara.

But some of Mary's family members feel so strongly in Kaitlyn Conley's innocence, they've started the Free Kaitlyn Conley campaign.

"The fact of the matter is there were three suspects initially," said David King. "It was William Yoder, Adam Yoder and Kaitlyn Conley. I couldn't help but question what sort of investigation can you really conduct if you've forced your hand to only pursue one person?"

And Mary's family members say Bill's alleged affair should have been enough for cops to investigate him further.

Crime Watch Daily spoke to Mary's sister Sharon over the phone.

"He was found to be with another woman," said Sharon Mills. "Later we found out it was our older sister Kathy."

Do you think Bill's relationship with Kathy began before Mary died?

"Yes, I do," said Janine King. "Relationships don't just start overnight. A neighbor testified that she had seen Bill over at Kathy's house, and she witnessed this, was testified to, a passionate kiss and embrace between them while she and her daughter were walking by."

Bill and Kathy are a couple now, but in court both testified their romantic relationship did not start until months after the murder.

Then there's Mary's son Adam. The sisters claim he was on the outs with his mother around the time she died.

"Mary and he had a falling out," said Janine. "Mary had been an enabler, but she was starting to take a firmer stand with him in that, and not giving him money."

Crime Watch Daily reached out to both Bill and Adam Yoder to get their responses to these allegations. So far they have not gotten back to us.

We caught up with the lead investigator on the case to get his reaction to the claims made by Mary's family members.

Are you certain that you have the right person there?

"I'm absolutely sure we got the right person. All the evidence came back against Kaitlyn Conley," said Oneida County Sheriff's Lt. Robert Nelson. "We interviewed Bill, we interviewed Adam, this was a long six-month investigation. We talked to a lot of different people, everybody had the opportunity to speak to us and tell us what their theories, their thoughts were. Over at the evidence at the end, nothing came back on Bill, nothing came back on Adam, everything came back on Kaitlyn Conley."

Kaitlyn Conley's defense team will be given the opportunity to appeal her conviction.

What do you and your family have to gain by coming on national television here in defense of Kaitlyn Conley?

"To exonerate her in the public eye, that it will help with the appeal," said Janine King.

Kaitlyn Conley is currently serving a 23-year sentence for first-degree manslaughter. But no matter how much time Kaitlyn spends behind bars, Mary Yoder's family is forever divided over her guilt or innocence, and is left mourning the loss of one of their beloved members.