Cause of death undetermined for former Marengo woman whose body police discovered in U-Haul unit

A cause of death is undetermined for a 33-year-old former Marengo woman whose boyfriend faces first-degree murder charges tied to her death and disappearance.

Potential causes of Michelle Arnold-Boesiger’s death include a drug overdose, asphyxiation, or a combination of the two, according to the woman’s autopsy report. Any of those possible scenarios could have been either accidental or homicidal, according to the report.

The Northwest Herald obtained the report Tuesday after Illinois Attorney General’s Office Public Access Bureau issued an opinion on Oct. 22, finding the Winnebago County Coroner’s Office did not meet its burden in denying the Northwest Herald’s request for records related to Arnold-Boesiger’s autopsy.

Michelle Arnold-Boesiger died more than three months before police discovered her body on March 2 inside of a car stored in a Roscoe U-Haul shed, investigators have said. The woman’s boyfriend, 34-year-old Jonathan Van Duyn, is charged in Winnebago County with first-degree murder and concealment of a homicidal death in connection with Arnold-Boesiger’s death.

[ Timeline of Michelle Arnold-Boesiger's death and disappearance  ]

Although the woman’s autopsy cited a post-mortem abrasion on her neck, Arnold-Boesiger’s body showed no significant injuries or diseases, according to the report.

Family and friends have previously said that Arnold-Boesiger suffered from Lupus.

The results of a toxicology test additionally showed “dangerous combinations of drugs,” including painkillers, alcohol, THC and antidepressants, in Arnold-Boesiger’s system. How much of each substance she ingested, however, is unclear. The length of time between Arnold-Boesiger’s death and autopsy rendered those results “unreliable,” forensic pathologist Mark Peters wrote in his report.

Van Duyn remains in Wisconsin, where last week a judge sentenced him to prison in connection with a separate set of allegations. Van Duyn pleaded guilty in that case to interfering with child custody after abducting his daughter in Walworth County. Investigators located the father and daughter in Indiana about three days after the girl’s mother reported her missing.

When police searched the camper where the pair was staying, they discovered writing on the walls and in one of Van Duyn’s journals that referenced Nov. 15, 2020, as the day he “was finally free,” according to court documents. Prosecutors in Winnebago County have since alleged that Nov. 15 is the same day Van Duyn killed Arnold-Boesiger.

The Winnebago County autopsy report additionally noted that “a suspect told his daughter that he killed (Arnold-Boesiger) and hid her body.”

Van Duyn remained in custody Thursday in Wisconsin. Prosecutors in Winnebago County said Friday that they planned to submit an extradition request this week to have Van Duyn transported to Illinois.