GHB is undetectable, so it leaves no trace in a drugging.

The word undetectable comes from forensic science itself. A 2004 paper on hair testing put it in its title, Testing for the undetectable in drug-facilitated sexual assault, and its abstract says: “Hair was suggested as a valuable specimen in situations where, as a result of a delay in reporting the crime, natural processes have eliminated the drug from typical biologic specimens”.[1]

GHB is detectable, for a short time. A 2015 review: “With an analytical detection limit of 1 mg/L, the detection window of GHB in serum was 4-5 h compared with 8-10 h for the analysis of urine”.[2] In eight volunteers, “Only 1.2 +/- 0.2% of the dose was excreted, resulting in a detection window of 720 min”.[3] The German review of knock-out drugs gives up to 8 hours in blood and up to 12 in urine, adding a second difficulty, “its physiological occurrence in the body”.[4]

That window is shorter than the time most people take to reach an examination. In one Australian series “The median delay from alleged incident to time of examination was 20 h.”[5] The 2015 review: “If more than 10-12 hours have elapsed after the alleged attack there is little hope of detecting and measurable amounts of GHB”.[2]

Hair is the exception. A French team showed in 2003 that “a single exposure to GHB in a case of sexual assault can be documented by hair analysis when collected about one month after the crime”.[6] So the fair version of the claim is that GHB is easily missed, not that it cannot be found.