He doesn’t want them to look at his son. He wants to protect his son AND himself! That’s why he kelpt claiming to be searching for her killer.
I understand that. However, if the police were focused on him and his DNA, if he kept saying over and over he was innocent they would only have moved to his son - so there is no way he was trying to protect his son or he would have just said he did it. ANY move away from him could have turned toward his son.