"Reasonable suspicion," not the more exacting "probable cause," is threshold requirement for an investigatory traffic stop, the Illinois Supreme Court held in a recent DUI ruling.

In overturning a trial court's order to suppress evidence in a Will County DUI case, the Illinois Supreme Court determined that a traffic stop was proper when the arresting officer witnessed the driver making slight deviations from his lane of traffic.

The trial court had granted the defendant's motion to suppress based on arguments that the evidence of his insobriety and suspended license was the "fruit of an unlawful search," and a divided appellate court affirmed that ruling. According to the high court's opinion, the defendant argued that the officer lacked "probable cause" and therefore had no proper grounds to make the traffic stop.

In People v. Hackett, 2012 IL 111781, a unanimous supreme court overturned the appellate and trial court decisions and remanded the case for a trial based on evidence stemming from what the court held to be a justified "investigatory stop" of defendant's vehicle. Reasonable suspicion, not probable cause, is the proper standard for an investigatory traffic stop, the high court held.

Assistant Appellate Defender Kerry Bryson said there was obviously some doubt in the minds of the trial judge and appellate panel about what justified pulling over a driver and investigating him and his vehicle.

"To the extent there might have been any question about that, the [supreme] court has made it clear that there shouldn't be," said Bryson, who did not handle this case. "To the extent that this is a concern, what clients ought to know moving forward is if they're going to challenge the stop, the proper standard is…was there reasonable suspicion."

'[M]omentary crossings' can justify stop

In affirming the motion to suppress, the appellate court relied on People v. Smith, 172 Ill.2d 289 (1986), in which a driver was convicted after driving in and out of multiple lanes of traffic for a "reasonably appreciable distance." The appellate court distinguished Smith from the case at hand, stating that Hackett made only "momentary crossings" of a highway lane line and therefore the officer lacked reasonable grounds to make a stop.

The supreme court rejected the notion that the distance or length of time of the lane deviations made any difference in the enforcement of a statute that prohibits any improper lane usage.

"Although this court in Smith…mentioned the measure of defendant's deviation into an adjacent lane and the distance he travelled therein, nothing in this court's analysis indicated either was significant to the outcome," Justice Karmeier wrote for the court in Hackett.

In this opinion, the supreme court's analysis focused on "the loose terminology the parties and lower courts in this case have used with reference to the standards applicable to the fourth amendment issue presented for our consideration. The question we agreed to address…is 'whether the appellate court erroneously found there was no reasonable suspicion for a traffic stop where the uncontested testimony showed defendant swerved twice across a lane divider of traffic.'"

The court explained that vehicle stops are subject to the Fourth Amendment's "reasonableness requirement," and the decision to stop a vehicle usually requires probable cause for an officer to believe that a traffic violation has occurred.

"However, as this court has observed, though traffic stops are frequently supported by 'probable cause'…as differentiated from the 'less exacting' standard of 'reasonable, articulable suspicion' that justifies an 'investigative stop,' the latter will suffice for purposes of the fourth amendment irrespective of whether the stop is supported by probable cause," the court wrote.

An opening for the defense?

Bryson said the Hackett case got interesting after the third district appellate court affirmed the motion to suppress "because it gave some support to challenging a traffic stop when there was just momentary drifting over the line." But now it is clear that multiple deviations from a lane of traffic, even if slight in distance and time, are sufficient grounds for an investigative stop, she said.

"I think there's a little more to it if you read [the Hackett decision] in depth," Bryson added. "There has to be no reasonable explanation for the deviations" in order for an investigatory stop to be justified.

"If there is a reason for the deviation from the lane, then there might not have been reasonable, articulable suspicion to justify the stop," Bryson said. "In some cases, there's been no exploration of that aspect of the basis for the stop. I think that leaves this open as for what a defense attorney can be looking for as a way to challenge the stop."

The supreme court bolstered its decision by pointing out that a police officer "can effect a lawful Terry stop without first 'considering whether the circumstances he or she observed would satisfy each element of a particular offense.'"

Where, as in Hackett, a police officer observes multiple lane deviations for no apparent reason, an investigatory stop is proper, the court reasoned.

"For probable cause and conviction, there must be something more: affirmative testimony that defendant deviated from his proper lane of travel and that no road conditions necessitated the movement," said the court. "An investigatory stop in this situation allows the officer to inquire further into the reason for the lane deviation, either by inquiry of the driver or verification of the condition of the roadway where the deviation occurred."