Female doc’s manner of death labeled ‘undetermined’ after lethal mix of drugs was found in her system when she died alone in the home of her firefighter boyfriend – three years after his previous fiancé was found shot dead

A female doctor died from a deadly mix of drugs, but the manner of death has been ruled ‘undetermined’ as the mystery surrounding her death grows.

Dr. Sarah Sweeney, 39, was found dead Jan. 13 at the home of her fiancé, local fire chief Robert Daus, in suburban St. Louis.

On Tuesday, a toxicology report from the St. Louis County Medical Examiner’s Office revealed the doctor’s cause of death was drug intoxication, but the manner has not yet been determined. Oxycodone, the epilepsy and pain medication Gabapentin and antihistamine Diphenhydramine were found in Sweeney’s system.

‘Dr. Sweeney was found with no apparent signs of trauma on her body, and our investigation at this time supports that she was home alone leading up to her death,” Frontenac police said.

She is the second woman engaged to Daus to die in recent years. Grace Holland was found dead from a gunshot in 2020. Her death was initially ruled a suicide, but the Netherlands investigation remains “active,” authorities said.

Sweeney, 39, was found dead on January 13 at the home of her fiancé, local fire chief Robert Daus (pictured), in suburban St. Louis.

Sweeney was the second woman to die while living with and engaged to Daus. Grace Holland (right) died of a gunshot wound to the head on July 22, 2020 at the Daus home

Following Sweeney’s death, police reopened the investigation into Holland’s death in July 2020 and their investigation ‘remains active’.

Daus, a captain with the Maryland Heights Fire Department, has yet to be identified as a suspect in either case and has denied any involvement in their deaths.

A native of West Virginia, Sweeney moved to Missouri to open her own podiatry practice in Creve Coeur.

Her mother, Teresa Sweeney Light, said: “We wish we could have her back. We just want closure, we want it to be truthful and honest, and right now we’re still in shock.”

According to her mother, Daus and Sweeney met while she was working in the emergency room, shortly after she moved to St. Louis.

‘Sarah was a lively and outgoing person who never met a stranger. She loved dogs and cats, and over the years rescued and owned several of them,” her obituary said.

‘Sarah was diagnosed with Perthes disease when she was six years old, which has left her experiencing a lot of physical pain throughout her life.’

Federal court documents reviewed by DailyMail.com revealed that Sweeney lived in fear of Daus, describing him as “suspected of the murder of a previous girlfriend.”

Sweeney’s claims emerged in lawsuits that are part of a lawsuit she filed in November 2022 against her former employer Best Foot Forward and founder Dr. Franklin Harry.

Federal court documents reviewed by DailyMail.com show Sweeney lived in fear of Daus, describing him as ‘suspected of the murder of a previous girlfriend’

Following Sweeney’s death, police reopened the investigation into Holland’s death and their investigation ‘remains active’

Sweeny emailed a friend: “But guess what, Danielle? I’ve been homeless, I’ve had to move in with my ‘killer’ boyfriend which was scary at times, I’ve lost every penny and canceled my savings account, I’ve had trouble finding a job from my past connection with him , I have suffered…I have experienced the ringing.”

Holland’s family has filed a wrongful death lawsuit claiming Daus is liable for Holland’s death and that he was psychologically and physically abusive.

Daus was never charged in connection with Holland’s death, which was ruled a suicide by the medical examiner, despite several key factors that, her family say, contradict that finding.

They point out that Holland was right-handed and, as a woman trained to use firearms, had always shot with her dominant hand.

Yet she was shot in the left temple – a feat described by her family as “inconsistent” with a self-inflicted wound and “consistent” with someone standing in front of her shooting her.