A US woman accused of trying to fatally poison her romantic partner is being held on US$1 million ($1.5 million) bail.

Connecticut state police arrested Kristen Hogan and charged her with attempted murder for allegedly mixing ethylene glycol, an ingredient found in antifreeze, into wine the victim drank and making him desperately ill at their home in Ridgefield.

Court records show Hogan, 33, and the victim, 34, were at the time in a bitter custody battle involving their two-year-old child.

Kristen Hogan is accused of trying to kill her partner with poisoned wine during a custody battle in the US. (Connecticut State Police)

“I’d like to say in all my years as a prosecutor that I’ve seen everything,” Richard Colangelo, a former prosecutor and current associate professor at the University of New Haven, who reviewed the arrest warrant, said.

“But this is one of those, it’s like, I thought I saw everything but I really didn’t.”

Investigators believe Hogan applied for a court hearing in August and, when her ex was at the Danbury courthouse, she allegedly went to the home they own together and slipped the chemical into a bottle of wine in the refrigerator.

Two days later, the victim drank the wine and within hours was at Danbury hospital, where doctors eventually put him on dialysis for glycol poisoning.

Lab results confirmed the poisoning on September 30 and police accessed records for Hogan’s smartphone.

“There were searches for different chemicals. How much of a certain type of chemical could kill you,” Colangelo said.

“You could kind of see the mindset and the planning that was going on.”

Hogan eventually admitted to putting the poison in the wine bottle, claiming she “just wanted to make him sick,” according to police.

She is due back in court on October 9.

Dining and Cooking