Hi MiizzCarmen,
I'm having trouble understanding what you are asking. Are you asking whether the DHS investigation into who should have custody of the child is separate from any investigation into s*xual assault against one of the parents?
If so, the two investigations are different as they ask different questions. The DHS' job is to determine what is in the best interests of the child. While the police's investigation is to determine whether person X committed the alleged s*xual offence against person Y. They will be separate and different investigations.
However, if person X is found to be guilty of the offence against person Y, this may be used against person X if person X wishes to have custody or some sort of parenting relationship with the child. In this case, the DHS will consider whether it is in the child's best interest to have a relationship with someone convicted of a s*xual offence. In other words, the conviction against person X will go toward his/her character in the DHS investigation.