JANESVILLE, Wis. -- The trial for the Rock County man accused of killing a woman and her two children in their mobile home near Janesville three years ago continued on Saturday.

Defense attorneys began presenting their case and the ex-wife of defendant James Koepp and her family took the stand. The defense hopes it can provide enough evidence that someone other than Koepp could be responsible for these killings, WISC-TV reported.

Saturday was the first time the defense called witnesses and they're trying to paint Koepp in a more positive light.

Defense attorney Walter Isaacson depicted Koepp as a softer, nurturing family man.

Jennifer Himes, the wife of Koepp's then-stepson, said Koepp was babysitting her children earlier the afternoon before the slayings took place.

"Was Jim making cookies with the kids at that point?” asked Isaacson.

“Yeah, Nancy (Koepp's wife at the time) had made a batch of cookies before she went (to work), and then they cooked them. They were putting them all out. So yeah, they baked them," answered Himes.

The defense has argued that the victim Danyetta Lentz and her two teenage children, Nicole and Scott, were killed by an unknown assailant in a botched robbery attempt.

Koepp's ex-wife, Nancy Kunkel, testified that a suspicious SUV was located near the Lentz home when she returned from work after midnight the night the family was slain.

"The reason why I noticed it is it was parked right in the middle of the road and as I went around, I was going, 'Jerk!' But, there was nobody in the car," said Kunkel.

The defense attorneys didn't elaborate beyond the suspicious vehicle.

In cross-examination, prosecutors argued that if indeed that SUV was there, it might not necessarily have been at the Lentz's home.

During Kunkel's testimony, deputy district attorney Perry Folts pointed to a general location on a map of the Janesville Terrace Mobile Home Park.

"Somewhere in there, somewhere," said Kunkel, in response to Folts' questions.

"Somewhere in there, but you're not exactly sure? And there's other buildings along this side of the road, right?" said Folts.

"Yes," answered Kunkel.

"And there's other trailers on the same side of the road as the Lentz's live, right?" asked Folts.

"Yes," answered Kunkel.

While the defense argued to support its own theory, the prosecutors' questioning of Koepp's ex-wife supported its motive that Koepp killed the Lentz family to hide an affair he had with Danyetta Lentz.

"Your marriage was over if you found out that he was cheating on you, correct?" asked Folts. "He knew that when you went into the relationship?"

"Yes," answered Kunkel.

Both the prosecution and defense argued that separate witnesses -- Koepp's former mother-in-law Himes -- heard nothing the night of the slayings. No screams and no calls for help were heard, they said.

Early next week, the defense will call its own DNA expert and several inmates from the Columbia Correctional Institution, where Koepp is currently serving a separate prison sentence.

Stay tuned to WISC-TV and Channel 3000 for continuing coverage.