Officials said the "shank" was a toothbrush with a nail file attached to the tip.
A jury is hearing arguments in the death penalty phase of Richardson's trial.
The same jury convicted him of torturing and murdering 4-year-old Teghan Skiba last week in under an hour.
In July 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. Richardson was found guilty of first-degree murder, felony child abuse, kidnapping, and sexual offense with a child.
Closing arguments will begin Thursday and then it will be up to the jury to decide whether Richardson will get life imprisonment or a death sentence.