Thirty-seven-year-old Brian Cooper is on trial for the second time in the strangulation death of 21-year-old Alisha Bromfield, who was six months pregnant.
Cooper and Bromfield, both from Plainfield, Illinois, were in Door County for the wedding of Cooper's sister in August 2012.
The first trial ended with a hung jury.
Connie Cooper testified Thursday her son was severely beaten as a child by her husband at the time, Patrick Cooper.
The Door County Advocate says the defendant's mother described the relationship between her son and Bromfield as platonic.
Brian Cooper is charged with two counts of first-degree intentional homicide.