PLYMOUTH, Mass.— Neal D. Barnard, MD, FACC, a noted expert on casomorphins which are naturally occurring opiates that can cause postpartum psychosis, says that in the Lindsay Clancy murder trial, a key piece of evidence is missing because it was never gathered. Apparently, she did not have a spinal tap. Natural opiates that originate in breastmilk may have passed into Clancy’s bloodstream and cerebrospinal fluid, possibly affecting her brain.