A disturbing new allegation has emerged in the case against Corie Walsh, the Illinois mother accused of killing her 2-year-old son Barrett: prosecutors say she also spoke about poisoning her husband when he returned home.

Corie Walsh is seen with her family in an undated photo posted to Facebook. Walsh allegedly killed her 2-year-old son before trying to harm herself inside the family’s Frankfort, Ill., home.Facebook/Corie Walsh

The allegation was disclosed during Walsh’s first court appearance on Tuesday, as prosecutors argued that the 40-year-old mother of four should remain detained before trial. Her defense team, meanwhile, painted a sharply different picture, saying Walsh was experiencing a severe psychotic episode and needed immediate psychiatric treatment.

Walsh faces three counts of first-degree murder in connection with Barrett’s death at the family’s home in Frankfort, Illinois, on September 1.

Her case has attracted widespread attention because witnesses told investigators that Walsh had become deeply invested in the Lindsay Clancy murder trial and was discussing it with friends only hours before Barrett was found.

But Walsh’s lawyers have strongly rejected attempts to characterize her as a Clancy “copycat,” arguing that her behavior should instead be understood in the context of what they describe as a serious mental-health crisis.

Prosecutors reveal alleged plan involving husband

Corie A. Walsh is facing three first-degree murder charges after prosecutors say her 2-year-old son was found with a ligature around his neck in the basement.WILL COUNTY ADULT DETENTION FACILITY

Among the most significant new details presented in court was an allegation involving Walsh’s husband, who was away from home when the incident occurred.

Prosecutors said Walsh made statements indicating that she intended to harm him after he returned, including a reference to poisoning him with a drink. They also noted that there were drinks and multiple prescription bottles inside the home.

Prosecutors further alleged that Walsh believed she had killed her other three children as well.

Those children were physically unharmed. An 8-month-old infant was inside the house at the time, while two school-aged children returned home as events were unfolding and went to a neighbor for help.

The neighbor then rushed into the house, found Barrett in the basement and attempted CPR before emergency responders arrived.

The 2-year-old was later pronounced dead at a hospital.

Walsh was discovered elsewhere inside the home with injuries authorities described as self-inflicted. She was taken for medical treatment.

The Will County Medical Examiner’s Office determined that Barrett died from asphyxia.

Defense says Walsh was suffering from psychosis

Defense attorney Robert Kerr told the court that Walsh was “severely mentally ill” at the time of the incident.

According to Kerr, doctors who evaluated Walsh after she was hospitalized recommended that she receive immediate treatment. He said she had been diagnosed with “brief psychotic disorder.”

Her attorneys argued that her mental condition is critical when considering statements she allegedly made to police, hospital staff and others after Barrett’s death.

Prosecutors have alleged that Walsh told authorities she harmed her son because she believed he was the “devil” and the “anti-Christ.”

The defense maintains that those comments came while Walsh was experiencing psychosis.

Her lawyers asked that she remain in an inpatient medical setting, while prosecutors argued that treatment could be provided while she was detained.

The judge ultimately ordered Walsh held before trial, finding that she posed a potential risk to her husband and remaining children.

Friends noticed a change hours earlier

The Lindsay Clancy case became part of the investigation after prosecutors said Walsh had recently become “very invested” in Clancy’s trial.

Witnesses said she had been actively discussing the case in a group chat with friends until only hours before Barrett was discovered.

But additional testimony presented in court provided more context about those conversations.

Friends reportedly noticed a dramatic change in Walsh’s messages that day, describing them as confusing and out of character.

At one point, Walsh appeared convinced that Clancy’s husband — rather than Clancy — had killed their children. In another message during jury deliberations, Walsh wrote that she was “really freaking out.”

People who encountered Walsh after the incident also described behavior they considered unusual.

A neighbor said Walsh appeared unlike herself, while a first responder reportedly described her as incoherent during the ambulance journey.

Her defense attorneys also said Walsh had recently seen a counselor and that family members and friends reported no previous signs that she had abused her children.

Lawyers reject ‘copycat’ characterization

Because Walsh had been following the Clancy proceedings so closely, comparisons between the two cases quickly emerged.

Her defense team has pushed back strongly against that narrative.

“Describing Corie to a copied Lindsay is to take an easy bait,” Kerr told the court, calling suggestions that Walsh was a Lindsay Clancy “copycat” “sickening.”

No evidence presented publicly has established that the Clancy case caused Walsh’s alleged actions.

Instead, the defense is focusing on Walsh’s mental state and the unusual behavior witnesses say they noticed in the hours before Barrett’s death.

Clancy’s case had drawn intense national attention because of the central dispute over her mental state. Her defense argued that she was suffering from postpartum psychosis when she killed her three children, while prosecutors maintained that despite her severe mental illness, she could understand and control her actions.

Husband continues to support Walsh

Another striking detail emerged during Tuesday’s hearing.

Walsh’s husband was not present in court, but officials said he has cooperated with police and social workers during the investigation.

Despite prosecutors’ allegation that Walsh had spoken about poisoning him, her defense attorneys told the court that both her husband and her mother continue to have “unwavering love and support” for her.

The hearing took place on the same day Barrett, affectionately known as “Bear,” was laid to rest.

Walsh remains detained as the case proceeds, while her attorneys continue to emphasize psychiatric treatment and prosecutors pursue the murder charges against her.

Her next scheduled court appearance is September 24.