Power." Usage in medicine In medicine, the term sine qua non (in contrast with pathognomonic) is often used in regard to any sign, symptom, or finding whose absence would very likely mean absence of the target disease or condition. The test for such a sign, symptom, or finding would thereby have very high sensitivity and thus would rarely miss the condition and so a negative result should be reassuring since the disease being tested for is absent. Examples include: The absence of finding the corresponding underlying mutation excludes certain types of hereditary colon cancer. A vaginal pH of less than 4.5 practically excludes bacterial vaginosis. Sine qua non was the inspiration behind a brand name of a tricyclic antidepressant manufactured in Germany: (Sinequan) doxepin. "But-for" causation in law In legal matters, "but-for", "sine qua non", causa sine qua non, or "cause-in-fact" causation, or condicio sine qua non, is a circumstance in which a certain act is a material cause of a certain injury or wrongdoing, without which the injury would not have occurred. It is established by the "but-for" test: but for the act having occurred, the injury would not have happened. The defendant's negligent conduct is the actual cause of the plaintiff's injury if the harm would not have occurred to the plaintiff "but for" the negligent conduct of the defendant. (Perkins) This type of causation is often contrasted with substantial-factor causation. The substantial factor test is used when there are multiple negligent tortfeasors which either (1) all caused the injury, in which case any and all of them are 100% joint and severally liable (treated as the group but suing the money) and the charged defendant would have to implead or sue the others to square the damages, or (2) only one could have actually caused the injury but they were all negligent in the same way and that one cannot be determined, in which case the burden shifts and any of them that cannot show their negligence was not the cause is 100% joint and severally liable. The purpose of this is allow the aggrieved party to get their damages, and make the negligent tortfeasors square up amongst themselves. See e.g. Hill v. Edmonds (N.Y., 1966); Anderson v. Minneapolis, St. P. & S. St. M. Ry. Co. (Minn., 1920) In Rogers v. Bromac Title Servs. LLC, the United States Fifth Circuit interpreted the language of the Jury