Sept. 30, 2025, 9:13 PM EDTBy Tim StellohThe sister of a Texas man whose wife allegedly killed him with a fatal dose of insulin testified Tuesday that before his 2023 death she’d grown increasingly worried about him after learning of Sarah Hartsfield’s ominous past.Jeannie Hartsfield took the stand in a courtroom east of Houston on the first day of testimony in Sarah Hartsfield’s murder trial in the death of Joseph Hartsfield, 46, and described learning of an alleged murder plot targeting another husband.The revelation came after Sarah Hartsfield, who has pleaded not guilty in Joseph Hartsfield’s death, disclosed to her sister-in-law that she’d also fatally shot a former partner in self-defense, Jeannie Hartsfield testified.Sarah Hartsfield in court.Rebeccah Glaser / DatelineThe sibling initially didn’t think much about the self-defense shooting, she testified. But she said she grew very concerned after Sarah Hartsfield told her that she’d been investigated by the FBI in an alleged murder plot.“Things didn’t seem right,” Jeannie Hartsfield said from the stand. More on Sarah HeartsfieldAfter 5-time bride is charged in husband’s murder, other deaths get a fresh lookSarah Hartsfield’s marriages and romances often ended under grim circumstancesMurder suspect’s son has been waiting for his mom’s arrest his whole lifeHartsfield fatally shot her fiancé in 2018The apparent plot referred to allegations that Sarah Hartsfield attempted to enlist her fourth husband to kill her third husband’s new wife in Sierra Vista, Arizona.The allegations, which Sarah Hartsfield has denied, were made by the third husband, Christopher Donohue, in an affidavit in support of a protection order that he filed in 2021. The fourth husband, David George, has said that he had no intention of carrying out the murder.A spokesman for the Sierra Vista Police Department has previously said a federal agent asked the department to monitor Donohue’s home with a “close patrol.” No charges were filed in the case. The FBI has not commented on the case.Donohue and George have both been subpoenaed to testify in Sarah Hartsfield’s murder trial.The self-defense shooting referred to the 2018 killing of Sarah Hartsfield’s fiancé, David Bragg. During a bond hearing in 2023, Sarah Hartsfield testified that she fatally shot Bragg in self-defense after an argument over her third husband’s decision to visit their children in Minnesota outside of normal visitation. After Sarah Hartsfield’s indictment in Joseph Hartsfield’s death, the county attorney who cleared her in Bragg’s killing — he previously said she had “no reasonable possibility of retreating” — said the case was “active” again. Victim Joseph Hartsfield.KPRCDouglas County Attorney Chad Larson has not responded to requests for comment on the status of that investigation.Tuesday’s testimony came after prosecutors began laying out their case against Sarah Hartsfield, described by Chambers County Assistant District Attorney Mallory Vargas as a performer whose “true identity” was concealed by her whirlwind relationship with Joseph Hartsfield.Within a year, the prosecutor said, the pair’s relationship had soured. As Joseph Hartsfield was preparing to leave her, Vargas alleged, Sarah Hartsfield intentionally caused his death.Officials have said that Joseph Hartsfield — who had diabetes — died on Jan. 15, 2023, from complications of toxic effects of insulin, the life-saving medicine that helps regulate blood sugar and has been used as a difficult-to-detect murder weapon. Joseph Hartsfield’s manner of death was listed as undetermined. Defense lawyer Case Darwin said that prosecutors were “telling a story” and suggested that Joseph Hartsfield’s death could be linked to poor management of his health issues. He didn’t take care of himself, Darwin said, and he’d previously been hospitalized for diabetes-related complications. Joseph Hartsfield had administered his own insulin, Darwin said, and there was no evidence showing who gave him the fatal dose.Sarah Hartsfield talks a lot, Darwin said, and she is “adamant she didn’t do this.”Tim StellohTim Stelloh is a breaking news reporter for NBC News Digital.Susan Leibowitz contributed.