No they do not have to tell him. If DNA wa back that lead to further charges he wouldn't know at this point..and won't know until the GJ brings in charges to hold her on capitol murder. Then he still will not know any of the evidence until he files motions for disvoery of the evidence.
The prosecution has until November, her next hearing on these current charges, to come forward with more concrete chrges through the GJ if they want ot follow through with that route. That means they have time to get everything right and inorder. After she is charged with murder, not before , the defense can and will file motions to see what cards the prosecution is holding. To me, the defense talking about the DNA at this point tlees me they believe further charges will be coming....otherwise they wouldn't even discuss the DNA.