I would say this is all a moot point since prop 19 failed, however the issue of legalizing marijuana is certainly far from being over and therefore the arguments remain legitimate.
BigMike, in response to your question regarding field testing for marijuana DUI, yes there is a way to test.
Currently in California if you are stopped for suspicion of driving under the influence, whether alcohol, marijuana, methamphetamines, etc., the standard investigation involves a battery of field sobriety tests FST (one leg stand, walk and turn, etc.) which, based on your performance, the officer determines you level of impairment. This is all done prior to an arrest being made. If one is subsequently arrested for suspicion of DUI then you are required by California law to submit to a chemical test. For alcohol this is usually done with a breath test or a blood test. For anything else it is usually a blood or urine test.
Now we are all familiar with the concept of a ‘breathalyzer’ or such a device that can instantly determine your level of blood alcohol content BAC. There is no such device for testing for marijuana. However, that is not to say that there are not other tests which involve saliva, urine, etc. The problem is twofold. 1) you would have to get the court system to recognize the validity of such filed tests and 2) would it be a requirement to submit to such a test? Remember, in order to use one of those tests you would have to provide a sample of your blood, urine, etc. Normally the government/state/law enforcement can’t compel you to give such a sample without a warrant. Even a sample of your exhaled breath (for a ‘breathalyzer’ device) is not mandatory on the side of the road. Prior to an arrest anyone can decline to provide such a sample. Hell, even breath samples obtained voluntarily on the side of the road do not hold up in court as evidence. For that one needs to provide a required sample, after arrest, which is done on a completely different machine which meets court requirements (these requirements actually differ from county to county depending on the whims of the district attorneys).
