My point here has been that the above statement you made is wrong. You stated that a chemical is required to prove intoxication and that an officer's observations or FST are not good enough to prove either drug or alcohol intoxication. But the case law clearly states otherwise:
In presenting evidence sufficient to convict a defendant of driving under the influence of alcohol, the State need not present scientific evidence such as a Breathalyzer or blood test, (Diaz, 377 Ill.App.3d at 344–45, 316 Ill.Dec. 187, 878 N.E.2d 1211); rather, the testimony of a sole, credible police officer is sufficient. People v. Janik, 127 Ill.2d 390, 402, 130 Ill.Dec. 427, 537 N.E.2d 756 (1989). Evidence, such as a “defendant's breath smelled of alcohol” and that his eyes were “glassy and bloodshot” is relevant in convicting a defendant. Morris, 2014 IL App (1st) 130512, ¶ 20, 384 Ill.Dec. 173. Other relevant non-scientific evidence includes a defendant's speech, failed sobriety tests, (People v. Robinson, 368 Ill.App.3d 963, 983, 307 Ill.Dec. 232, 859 N.E.2d 232 (2006)), or his refusal to submit to a Breathalyzer test (People v. Johnson, 218 Ill.2d 125, 140, 299 Ill.Dec. 677, 842 N.E.2d 714 (2005)).
People v. Crawford, 2015 IL App (1st) 130031-U, ¶ 17 (Bolding added). As you can see from the part I bolded, the appeals court states point blank that a chemical test is NOT required, contradicting your statement that it is. In that case, the appeals court upheld the defendant's conviction on an alcohol DUI based on the following:
At trial, Cruz stated he smelled alcohol coming from defendant's breath, defendant admitted to Cruz that he had a beer around midnight and had just left a bar. Furthermore, Cruz stated defendant's eyes were “bloodshot,” his speech was “slurred” and he believed based on his years of experience that defendant had failed all three field sobriety tests. Finally, defendant refused to submit to a Breathalyzer test at the police station.
People v. Crawford, 2015 IL App (1st) 130031-U, ¶ 23. That stop was recorded on video, which the jury saw. So the conviction was based solely on what the officer testified he saw and heard during the stop, including the FSTs, and the video of it which backed up his testimony. Critically, for our conversation, there was NO chemical test involved at all. It was not required. All there was here was the admission of the defendant he'd been drinking, the cop's observations, and the FSTs. And the latter two of those you claim aren't good enough as evidence. Yet the court, in the quote above, says they are.
You complain that I used alcohol DUI as my example to rebut your statement, even though your statement itself referred to both alcohol and marijuana intoxication. But even with pot DUI, the courts don't insist on a chemical test. In affirming that there was probable cause for arrest and conviction on a pot DUI charge, a court stated the following:
Nonetheless, upon approaching the driver's side door of the Infiniti, Risteen detected the odor of burnt and unburnt marijuana emanating from the vehicle, and the odor of burnt marijuana coming from the defendant's person. Among other things, the defendant had red and glassy eyes, he was struggling to keep his eyes open and his head upright, “his coordination was slow,” he had difficulty “focusing,” and he also had difficulty in following the officer's “simple directions.” The defendant told the officer that he had smoked marijuana earlier that day, before he left to drive to Somerville. Given this, the judge was warranted in finding that police had probable cause to believe that the defendant had operated a motor vehicle while impaired.
Commonwealth v. Davis, 481 Mass. 210, 216–17, 114 N.E.3d 556, 564 (2019). You'll notice the evidence consisted entirely of the cop's testimony of what he observed of the condition of the defendant during the stop, the smell of burnt marijuana, and the defendant's admission that he had smoked pot earlier in the day. Again, no chemical test was required. The defendant got convicted of a marijuana DUI without any scientific evidence at all.
The cases I cited here are just two of the hundreds of cases I found for alcohol and marijuana DUI convictions in which there was a conviction without a chemical test. The case law clearly shows your contention that a chemical test is necessary is wrong.