Jackson called what Richardson allegedly did to the child "heinous, atrocious, cruel acts."
Jackson said Skiba was tortured, sexually assaulted, and beaten by her mother's boyfriend over a 10-day period while her mother, Helen Roxanne Reyes, was out-of-state for Army Reserves training in July 2010.
"It didn't end until he beat her brains so badly that she lost consciousness," said Jackson - asking jurors to find Richardson guilty.
In 2010, the then-21-year-old Richardson took Skiba to Johnston Medical - claiming the girl had fallen off the bed. However, doctors found she had cuts, bruises, a head wound, and bite marks on her body. Skiba died days later from her injuries after she was transferred to UNC.
In his closing argument, defense attorney Jonathan Broun called the case "tragic" and "sad" and told jurors that it would be natural for them to feel "disgust," "anger," and "hatred" after listening to testimony.
"You have to go beyond your natural and understandable instincts and get to the facts," said Broun.
Broun said Richardson never intended to kill Skiba. Instead, the attorney said Richardson shook the child so hard that it caused brain injuries, and then waited too long to get her medical help.
Broun also said that despite the injuries to Skiba's genitals, there was never any sexual intent on Richardson's part.
"That is not intended to lessen what happened, but there was no sexual intent," said Broun.
Broun also asked jurors to consider Richardson's background and mental state. The defense claims he was abused as a child by his father and had undiagnosed mental problems.
In his closing argument, Jackson asked jurors to find Richardson guilty. He's charged with first-degree murder, felony child abuse, kidnapping and sexual offense with a child. He could face the death penalty if convicted.