Illinois, as is the case with most states and the federal government, makes it illegal to possess marijuana. A few states recognize medicinal marijuana, which can be used with a prescription.
A couple of states recently decriminalized (made legal) marijuana use. A topic for another time is how those states will square their laws with the fact that marijuana possession remains a federal offense should the Federal Government choose to press charges.
That aside, driving under the influence (DUI) is illegal in all 50 states, including Illinois. 625 ILCS 5/11-501 While the term used is “driving” under the influence, the specific law makes it illegal, while “under the influence”, to drive or to be in “actual physical control” of a “vehicle” anywhere within the State of Illinois.
A “vehicle” includes any device upon which property or person may be transported, excluding human-powered devices. 625 ILCS 5/1-217 Therefore, it is not illegal to operate a bicycle while under the influence. People v. Schaefer, 274 Ill. App. 3d 450, 210 Ill. Dec. 968, 654 N.E.2d 267 (2 Dist. 1995) An ATV is, however, covered, even though you are not required to have a driver’s license or license plate to operate one.
“Under the influence” does not require the State to prove you were “drunk, intoxicated, buzzed” etc. Rather, a person is under the influence of alcohol when, as a result of drinking any amount of alcohol, his mental or physical faculties are so impaired as to reduce his ability to think and act with ordinary care IPI (Criminal) 23.29 In essence, you may convicted of DUI based upon nothing beyond proof that alcohol reduced your ability to think and act normally.
You may also be convicted of DUI in a way that does not require proof of actual impairment. If the state can show through chemical testing that your blood alcohol level at the time you were driving or in actual physical control of a vehicle was .08 or higher, you are just as guilty as though the State had proven your ability to drive was impaired due to alcohol.
In these blood-alcohol level type of cases, the defense must attempt to attack the manner in which the test was administered or assail its general reliability to prove accurate results, or otherwise show a judge or jury that the police engaged in other irregularities that tainted the evidence or that violated your Constitutional rights. While evidence of your apparent intoxicated or sober state are not required in this type of prosecution, such evidence can either support or erode the jury’s confidence in the chemical test results that the state proffers as proof of your being .08 or above.
The concept of actual physical control is the reason that the police doe not necessarily have to see you “driving” in order to support a DUI charge. The most common situation in which this non-driving issue arises involves a driver who is “sleeping it off” in a parking lot or roadside.
Contrary to what many seem to believe, there is no hard and fast rule one can lay down to make a definitive determination of the outcome. Factors such as in which seat you sleeping whether or not the keys were in or out of the ignition and whether the vehicle was running are all relevant but none is determinative. Ultimately it’s up the trier of fact (jury or judge) to decide what constitutes alcohol physical control. People v. Davis, 205 Ill. App. 3d 431, 150 Ill. Dec. 349, 562 N.E.2d 1152 (1 Dist. 1990)
Current Illinois law makes it illegal to operate a vehicle with “any amount” of marijuana in your blood, breath or urine. You smoked two days earlier and there’s still a trace of THC in your blood, breath or urine, you can expect a DUI charge.
It seems clear that if Illinois were to decriminalize marijuana, this provision would be repealed. That would not, however, create a legal right to drive high. Illinois already has a law that makes it illegal to drive under the influence of legal drugs.
What these cases often come down to is proving that the legal drug caused impaired driving. This involves so-called Drug Recognition Experts (DRE).
A non-expert can give an opinion as to whether someone is intoxicated. A police officer has been trained to spot it. There are recognized failed sobriety tests pertaining to alcohol. At present proof of drug impairment typically requires a DRE.