The nation’s largest organization for medical examiners has issued a warning about a controversial, centuries-old forensic test that has contributed to cases in which pregnant women have been charged with murder.

The premise behind the lung float test is simple: If a baby was born alive and then died, air from its first breaths would cause its lungs to float in a jar with water. If the baby was stillborn, the lack of air in the lungs would cause them to sink.

But the many critics of the test have long labeled it junk science and drawn parallels between the test and witch trials, where women were deemed witches based on whether they floated or sank.