If the drugs they claimed that she used were actually found in her system and if a test that actually works showed that the baby had been born alive.
The reasonable conclusion that she took the drugs is pretty definitely countered by the fact that none were in her system. The reasonable conclusion that the baby was born alive is rendered moot by the fact that the test they used simply does not work.
The argument is not that she took the drugs, her attempt to by the drugs establishes intent. In order for a crime to occur you need both
Act and Intent. So her attempt to buy the drugs establishes intent whether she bought them or not.
THen her subsequent action of throwing the baby away in the dumpster establishes the Act.
Intent + Act = Crime
It's very simple legal math. Then couple it with the circumstantial evidence and her actions afterwards and you can present a strong argument that this was a crime.
THere are two ways to look at the burden of proof in this case. You are saying, "Well, they can't prove the baby was born alive". I would counter that and say, "Well, she can't prove the baby was still born!!!"
Then I would also present the argument that if she would have called 911 immediately during her labor, the baby could have been born in a hospital and with care "could" have lived. Again, the burden shifts back to her, can she "prove" that the birth happened so fast that she couldn't call for help? An instant miscarriage at 25 weeks seems pretty unlikely.
I submit that since this case is about the death of another person, burden of proof shifts from the State to the Accused. It's not the State that has to prove the baby was born alive. No. It's the Accused that should have to prove the baby was born dead. And the Accused can't do that. Then couple it with the Intent and then you have Intent + Act = Crime. And thus she is guilty and i'm not losing any sleep over it.
You can try to make this case about a "miscarriage" but I don't buy it. 25 wks is not a miscarriage, it's a premature birth. There is a huge difference. And with medical treatment the baby could have survived and this mother denied the baby that through her willful negligence. So, when you are negligent and it results in a death, you get charge and convicted. If convicted you pay the penalty and if the penalty is harsh, so be it.