This test would be fine if we didn't have an adversarial system for expert witnesses. A jury can be made to understand that this test can produce false positives and should not be considered definitive evidence that precludes a reasonable doubt because it is reasonable that a stillborn baby's lungs can randomly get air in them from mechanisms other than breathing. It could still be useful for weighing the other evidence in the case.

The problem comes from the fact that the defense has to hire a competing expert to explain that everything the med examiner did was bunk and the jury has to decide what expert to trust, not what the value of the information is. That's not something a jury is particularly good at doing. Beyond that, who you hire ends up costing the defense money and can be a problem for indigent defendants.

I'll give you an example from the rape/murder charge that I was on a jury for that we put a guy away for life. A test was used to determine the time between ejaculation and murder as the defendant's argument was that he had sex with but did not murder the victim. A prostatic acid phosphatase test was used to determine that the semen was deposited shortly before the murder. That is also a test that isn't well studied, particularly in my case that involved a decomposing body.

His DNA and that test alone were not enough for me to reach beyond a reasonable doubt. The timeline of her disappearance, the fact that she was found near his camp, and the fact that the ligature used to kill her was from his camp was. The test just added to a growing list, where it was no longer reasonable to have a doubt.