Timothy Sanders, 40, had to submit a blood or saliva sample for a comparison analysis to determine if he's the father of 21-month-old Madison Dolford, the toddler shot and killed at a home on Belle Avenue in Hartsville on December 2.
Dolford's mother April Dixon, 23, and Sanders are both charged with Murder and Conspiracy in the child's death.
Police haven't released much information about the investigation, including a motive.
Court documents filed Wednesday say investigators have evidence that Sanders had obtained insurance from various companies claiming he was the child's father.
It says Sanders DNA is needed because it may further establish motive for the crime.
Arrest warrants say Dixon and Sanders had conspired since October 2 to murder the toddler.
Prosecutors say Sanders and Dixon will undergo mental evaluations. They didn't specify why those evaluations were relevant to the investigation.
Dixon and Sanders remain behind bars at the Darlington County Detention Center.