GHB has an "oxygen saving" effect. Say, if the person died of a heart attack - your body will produce GHB naturally to save yourself. I did a speech in college about GHB and did some research. I recall a study where a study was done on cadavers of old people who died of heart attacks (far from a "rave scene" or pretty unlikely to have gotten dosed for date rape)... and they were all found to have elevated levels of GHB.