A 12-person jury, which began deliberating the case since Wednesday, convicted Finn in the October 2016 death of 16-year-old Natalie Finn, according to the Des Moines Register.
Natalie weighed just 85 pounds (38 kgs) at the time of her death and one attorney described the case as the worst he had ever seen.
The mother of five will be sentenced Jan. 26, but first-degree murder carries a mandatory life sentence in Iowa.
In final arguments, the prosecution argued Finn sought to kill and torment the three children, including Natalie, who was adopted. The defense claimed Finn was detached from reality.
“In 18 years of being a prosecutor, this is the worst case I’ve ever seen,” Assistant Polk County Attorney Bret Lucas said after the verdict, as reported by CBS News.
Police said Natalie was found emaciated, unresponsive and wearing adult diapers when authorities responded to an emergency call at Finn’s home in West Des Moines, Iowa, on Oct. 24, 2016.
The teen was not breathing and was lying on the waste-covered linoleum floor of her unfurnished bedroom, investigators have said. Police believe the girl had been in her own excrement “for some time.”
Days before her death, two of Natalie’s siblings fed her water with a syringe and tried giving her yogurt, Finn’s son, Jaden, said in court during the first full week of testimony.
“They are worthless,” she allegedly wrote in a March 2, 2016, text. “I can’t stand them. … [I’m] so done with this s—.”
Finn’s ex-husband, Joe Finn, has pleaded not guilty to kidnapping, neglect or abandonment and child endangerment. He wasn’t living with the rest of the family when Natalie died. His trial begins Jan. 8.
This article originally appeared on PEOPLE