The injuries prosecutors say an 8-year-old boy sustained at the hands of his father and a woman who confined the boy in a basement have been detailed in court.

Pediatric nurse practitioner Ann Swisher said Wednesday one of the U-shaped marks on the boy's buttock was likely the result of him being spanked by a flyswatter.

Prosecutors wrapped up their case against 40-year-old Traci Tyler on Wednesday. The defense didn't call any witnesses. Both sides will submit written briefs before the judge rules likely sometime in March.

"Her specific intent was to break this kid," said Assistant Iowa Attorney General Laura Roan.

Swisher said during the bench trial that the other marks she observed on the boy were more difficult to identify because they were healing.

Prosecutors say Tyler and Alex Shadlow locked the boy in their home, in a space under the basement stairs, for at least nine hours a day in the summer of 2017. The two are both charged with kidnapping.

The boy told authorities he was required to sleep on concrete and use a tin cup for a toilet. Food was also withheld at times.

Prosecutors say Tyler also urged her dog to attack the boy, which left scars on his back and limbs.

School officials reported their concerns after the boy described his life at the home in Ackley, Iowa.

One of Tyler's attorneys, Ted Fisher, said she shouldn't be charged with a crime.

"We're not suggesting that putting a kid under the stair enclosure is good parenting ... but parents do have the right to inflict corporal punishment," Fisher said.

Shadlow's trial will start later.