A California woman whose infant son died with methamphetamine in his system will face a third murder trial, a Riverside County Judge ruled Monday. Amy Leanne Prien was convicted of second-degree murder in her son's death in 2003, but that conviction was overturned by an appeals court citing flawed jury instructions. A retrial ended in a mistrial in June after jurors deadlocked 6-6.

After the mistrial, Prien's lawyers moved to dismiss the charge, but Judge Patrick Magers declined. "It is abundantly clear to the court that the cause of death of the victim was methamphetamine intoxication," he said from the bench as he rejected the motion.

What is not so clear is where the meth in the child's system came from. Prosecutors have argued that Prien, an admitted long-time meth user, caused her child's death by feeding him her breast milk when she was using the popular stimulant. They argued that Prien continued smoking meth while breast-feeding, a charge she has consistently denied. She has suggested that a male guest in her home may have provided the drug to the baby.

A major problem for the prosecution is that the bottle of milk found beside the dead baby was misplaced by law enforcement and never tested for the presence of methamphetamine. And while Prien was tested and came back positive for meth, police never tested her breast milk. Los Angeles attorney Joe Reichmann, who is representing Prien, argued futilely that the charge should be dropped because it was based on "make-believe science" since prosecutors had no way of knowing the meth levels in her breast milk.

California prosecutors have repeatedly proven unable to make meth mother murder cases stick, and it is unclear why they are pursuing Prien with such a vengeance. It's not like she got off scot-free. In addition to losing her child, she is currently serving a 10-year prison sentence for felony child endangerment in the same case.