Craft's lawyers argued that the girls were coached by parents who suddenly had it out for Craft. They argued that the family of one of the girls was upset that Craft wasn't giving the girl better grades in class.
According to Welner, children are especially susceptible to the power of suggestion when it comes to memories.
"There's been some attention given to the question of false memory," he said. "Children can take in the suggestion of parents or authority figures and want to please them. Because parents are convinced something happened, they want it to [have] happened.
"I'm not saying this is a false memory. What I'm saying is the jury has a powerful question on them going both ways," he said.
One of their fathers told jurors that he wasn't making this up and neither was his daughter.
"And I'll never forget the look on her face or in her eyes -- she stopped everything she did and looked me dead in the eye and said 'I know it did, Daddy,'" said the father of one alleged victim.
The Associated Press contributed to this story.