Circumstantial evidence can certainly be sufficient evidence as regards satisfying the proof beyond a reasonable doubt requirement. However, strong circumstantial evidence (inculpatory evidence not collaborative evidence) would still have to satisfy the charges. For murder two, at a minimum, the State would need to prove malice aforethought. For murder one, the State would need to prove the added elements of willful, premeditated and deliberated.
Without a time of death, a place of death, a cause of death, a manner of death, an eyewitness, a crime scene, forensic evidence, a confession or a clear motive, I would not expect a GJ to indict Drew for murder. Nor would I expect the prosecutor to ask for such an indictment, for I can't see how the prosecutor could hope to prove a murder charge.
And, a change of venue would probably be in order. In no way am I indicating DP is innocent - just stating how difficult it would be to prosecute.