I think that the oral fluid screening devices are probably an aid to law enforcement because they give an almost immediate indication, usually within three minutes to five minutes. When pulling a blood sample or taking an oral fluid sample to send to a lab, you can wait weeks, if not months, to get a test result back. In order to make a case, I do believe that a police officer has to make careful observations and I think a judge or jury would like the corroboration that the person had ingested marijuana. The blood or oral fluid is simply indicating that there's evidence of marijuana use, corroborating an officer's observations.
On September 27th, 2017. See this statement in context.