I suspect Stern looked at Anna's family situation, especially the disturbing presence of 20 year old Daniel, who, between his drug binges, could see what Stern was, and decided to eliminate Daniel. Daniel, being a whacked out druggie, was a sitting duck for a lethal OD of any number of substances that could not be traced to Stern under circumstances where Stern couldn't raise a reasonable doubt about the drugs' provenance.
IMHO, having done Daniel so effectively, Stern then turned his attention to the even more drugged up and neurotic Anna and untraceably provided just the little bit of extra juice needed to bump her off. Now, if he's declared the baby's father or can produce a will that makes him Anna's beneficiary, he can cut a deal, settle Anna's lawsuit, and walk off with 20 or 30 million dollars.
"Stern was with Smith's son Daniel when he died from drug-related causes in Smith's hospital room on Sept. 10, three days after she gave birth to her daughter. He was accused by Smith's mother of supplying drugs to Daniel and went on Larry King's show on CNN, vehemently denying he did so.
Questions are likely to be asked of him again as he was on the scene when paramedics arrived to try and revive Smith,39, according to Captain Dan Fitzgerald of Hollywood Fire and Rescue."
There appears to be no drugs in Smith's bloodstream and the autopsy notes "blood in her stomach from trauma".