But you can find people guilty based on circumstantial evidence. They did with Scott Peterson.
Not reporting her missing for a month (and even then, she still didn't report it, her mom did), clearly happy her child was gone because she went out partying, looking up chloroform and neck breaking on the Internet, blaming her dad, blaming her brother, blaming the nonexistent nanny named Zanny, chloroform found in her car, "death smell" in her car.
She could have been found on something, anything other than lying.
Even if her story was true about her drowning... wouldn't that be neglect?