SPRINGFIELD — Prosecutors and defense lawyers agree recent case law says drivers don’t have to be impaired by the drugs in their system to be liable for crashes.

What they disagree about is whether the defendant can still bring evidence to try to rebut the presumption of impairment.

Both sides will get a chance to iron out the issue in front of Illinois Supreme Court justices this week.

The arguments in People v. Ida Way, slated for Tuesday morning, will help start the high court’s September term that begins this week.

It’s one of nine criminal and two civil cases the Supreme Court justices will be looking at over the next few days. Next week, they’ll hear arguments in two more criminal and eight more civil appeals.

Ida Way was charged with three counts of aggravated driving under the influence stemming from a crash she was involved in on Jan. 28, 2012. Her 14-year-old son, who was the passenger in her car, and a pregnant woman in another vehicle, were injured. Her son told police that his mother “fell asleep” just before the incident.

The state submitted that she was driving with marijuana in her system at the time of the crash, and a urine analysis showed she had THC in her system, a chemical associated with cannabis.

Prosecutors filed a motion in limine at trial in December 2012 saying that, according to the 2011 Illinois Supreme Court opinion in People v. Martin, they didn’t have to prove drug impairment was the proximate cause of the injuries in an aggravated DUI case involving illegal drugs — just that they were caused by Way’s driving.

Thus, they asked 20th Judicial Circuit Judge John Baricevic to prohibit Way from arguing there were other reasons she lost consciousness before the crash.

Way’s defense agreed the state didn’t have to prove she was impaired, but argued it would be unconstitutional if she wasn’t allowed to bring any evidence against the presumption of impairment.

The judge agreed with the state, ruling that the law established a system of strict liability in which a driver is responsible for the crash if there is any level of drugs in his or her system when it occurs. He ultimately ruled in a bench trial that there was evidence of the THC in Way’s blood, but there was not evidence she was impaired.

Still, he reiterated that proof of impairment was not necessary, and that there was sufficient evidence to find Way guilty on all three counts. He eventually sentenced her to 18 months in prison. But at the sentencing hearing, Way’s defense counsel said her physician would have testified that she has low blood-pressure, which could have caused her to lose consciousness.

At the 5th District Appellate Court, Way again stipulated that the state just had to prove her driving was the proximate cause of the crash, but argued that proximate cause is determined in part by whether the crash was foreseeable, and thus, she should have been allowed to bring evidence that an unforeseeable sudden illness caused the crash.

To bolster that argument, she pointed to a body of civil case law that delineates when an accident or injury is caused by “an act of God” — induced by “natural causes” that “could not be prevented by human care, skill and foresight.”

Whether such a condition occurs is almost always a question that should be argued before and resolved by the trier of fact, the 4th District Appellate Court said in the 2010 case, Evans v. Brown.

On that basis, Way argued, she should’ve been allowed to argue about her low blood pressure.

The 5th District panel, in a decision authored by Justice James R. Moore last year, agreed with that proposition. Although the state argued that it wasn’t aware of any criminal cases that utilized an “act of God” defense, the appeals panel wrote that the Supreme Court has often held there is plenty of overlap in civil and criminal cases regarding proximate cause when people are injured or killed.

The state’s highest court has “repeatedly employed the same definition of proximate cause, and the same general analysis regarding foreseeability, that we have outlined above, albeit without specifically incorporating the ‘act of God’ defense into criminal cases,” Moore wrote. “We see no logical reason, however, to bring part, but not all, of the civil law analysis regarding proximate cause into criminal cases, and the [s]tate has suggested none.”

The appeals panel also wrote that the Martin precedent, in which the court reinstated a DUI conviction for a man with methamphetamine in his system after a crash even though no tests could confirm his impairment, was of “limited relevance” to this case.

“[T]he Martin court was not asked to address the question before this court, which as stated above is what must be proved with regard to the proximate cause of the accident, and what kind of defenses a defendant may seek to introduce at trial in an effort to convince the trier of fact that the defendant’s driving did not proximately cause the accident in question,” the panel wrote.

Finally, the trio of judges wrote it was not harmless error for the trial judge to deny Way the opportunity to argue about a sudden illness. The state argued an alleged sudden illness could have been a secondary reason why her car crossed the center line and she got into a serious crash, but the “presumption of impairment” meant it could not have been the proximate cause.

Moore wrote that neither Martin nor any other decision has made such a “sweeping” statement, and that if a trier of fact decided Way had an underlying illness that was the proximate cause of the accident, she would prevail in her arguments. If the trier of fact decided there was no illness, or it was a secondary cause or one of many causes, the state would win.

“But that was for the trier of fact to decide, and it was not harmless error for the trial judge to rule otherwise,” the panel wrote.

Maggie Arina Heim, an assistant appellate defender who represented Way, could not be reached for comment this morning.

“I think really this just comes down to an interpretation of the Supreme Court’s decision in Martin about proximate cause,” said Sharon D. Shanahan, an appellate prosecutor who argued for the state at the appeals court and authored the appeal petition that was accepted by the high court. “Martin says that a driver with a controlled substance in his body violates the (Vehicle Code) simply by driving.”

The case is People v. Ida Way, No. 120023.