What to know about alleged Madison poisoning plot

After two days of hazardous materials investigations across the city, a 41-year-old Madison woman’s initial court appearance Wednesday broke open what prosecutors described as a plot to poison two women with cyanide.

Prosecutors accused the woman, Andrea L. Whitaker, of aiding 43-year-old Paul D. Van Duyne Jr., also of Madison, in attempting to kill the two women he briefly dated. Van Duyne will make his initial appearance Friday, when criminal complaints against the two are expected to be filed.

Here’s what we know so far about the case. 

Who are the suspects?

Van Duyne was booked into Dane County Jail on Sunday and faces tentative charges of attempted first-degree homicide and stalking. Whitaker was arrested Monday and faces tentative charges of harboring or aiding a felon.

Little is known so far about both suspects, and their exact relationship is unclear. Van Duyne earned a mechanical engineering degree from Princeton University, according to a flyer announcing his participation in a webinar hosted by the Wisconsin Healthcare Engineering Association in July 2024. After working as an engineer “designing chemical and pharmaceutical production facilities,” the flyer reads, he joined IMEG, an engineering firm .

A picture of domestic tumult around Van Duyne has emerged from county court records. On May 22, a judge ordered Van Duyne to have no contact with a woman he briefly dated after he allegedly broke into or tried to break into her vehicle while it was parked at the Costco store in Middleton on May 15 and May 20. Eight days later, a Dane County circuit judge ordered him to surrender any firearms he had to law enforcement.

In the petition for the harassment injunction, the woman wrote that she’d gone on two dates with Van Duyne in the fall of 2023 but then informed him she wasn’t interested in continuing the relationship. He contacted her again by text in February 2024 and then in May 2024, when he reportedly told her about a “difficult conversation involving boundaries with his ex wife.”

He and his former wife were divorced in July 2024, and they have two minor children.

Whitaker "has an academic background in pharmacology," Dane County Deputy District Attorney William Brown said at Whitaker’s bond hearing Wednesday. While Van Duyne is alleged to have attempted to poison the women, Whitaker "is likely the brains of the operation," Brown said.

What do prosecutors say happened?

According to prosecutors and court records: 

One of the women Van Duyne briefly dated was coming out of Costco last month when she saw people standing around her car. They told her her car had been broken into. Nothing appeared to be missing, but when she took a sip of water from the water bottle she kept in her car "it tasted terrible," and she spit it out. In a later visit to Costco, bystanders again told her someone had broken into her car. After smelling the water in her water bottle, she called police.

Police tied the break-ins to Van Duyne and sent the water bottle to the state Crime Lab, where analysts determined it contained cyanide.

Around the same time, a Janesville woman Van Duyne had briefly dated went to the gym and noticed the water in her water bottle had "a funny taste." She also noticed a powdery substance in her car. At some point, that woman was hospitalized for cyanide poisoning.

Police were able to place Van Duyne at both locations through his license plate and other tracking methods. At 11 p.m. Sunday, he showed up at the Janesville victim's house, which "forced everyone's hand" and prompted police to arrest him.

One of Van Duyne's first phone calls from jail was to Whitaker. Although court records list Van Duyne's address as 122 N. Spooner St. on the Near West Side, he appears to also have been associated with a residence at 1401 W. Skyline Drive. In his call to Whitaker, Van Duyne instructed her to remove evidence from the Skyline Drive address, including a computer, a box and other items.

Agents with the state Department of Justice's Division of Criminal Investigation had the home staked out, and when Whitaker began removing the items Monday morning, they arrested her. Among the evidence seized were Whitaker's phone, which contained chat messages with Van Duyne and an "extraordinarily concerning" search history including such terms as "calcium cyanide," "sodium cyanide," "potassium cyanide," "odor" and "lethal dose."

What's with all the hazmat teams?

In attempting to conduct search warrants, police on Monday first went to the Skyline Drive address. Due to the potential danger to investigators, teams of specialists with the Madison Fire Department, DCI, the FBI and even the National Guard were called in to assist, which made the searches "extremely slow going."

A second search was conducted on Tuesday at the Spooner Street address, and then a third later Tuesday in the 5600 block of Schroeder Road, where Whitaker has an apartment.

Over the course of the investigation, seven DCI agents were hospitalized. Their conditions are unknown.

What happens next? 

At her initial court appearance Wednesday, Whitaker was ordered held on $750,000 bail. Because the courts are closed Thursday due to the Juneteenth holiday, criminal complaints against the pair are expected to be filed on Friday, when Van Duyne is expected to have his initial court appearance.

Brown said he expected to file additional charges against Whitaker.