Are Passive Alcohol Sensors Legal at Illinois Traffic Stops?

 Posted on December 04, 2025 in DUI

Illinois law enforcement agencies are quietly adopting Passive Alcohol Sensors (PAS), which are handheld devices typically built into flashlights or other traffic-stop tools. These devices "sniff" for alcohol in the air around the driver. Aside from the fact that PAS devices detect ethanol without requiring a breath sample (raising the question of whether PAS use equals an unlawful search), there are no state standards for calibration, reliability, or officer training.

Currently, officers are not required to disclose the use of a PAS device, even though it often provides them with probable cause to administer a field sobriety test and/or a portable breathalyzer test. Essentially, the PAS is a device with no rules because it is not recognized under Illinois DUI statutes (625 ILCS 5/11-501) and is not admissible as evidence in a DUI trial.

PAS-based DUI stops are becoming a major battleground for Illinois defense lawyers. If a PAS device was used to justify a field sobriety test and you were charged with DUI, it is imperative that you speak to a knowledgeable DuPage County, IL criminal defense attorney.  

Understanding Passive Alcohol Sensors in Illinois

A PAS is a device that detects alcohol vapor in the ambient air. The device requires no blowing or consent and was designed to alert police to the presence of alcohol rather than impairment. Law enforcement uses PAS devices as a quick screening tool at traffic stops and roadside safety checks, as an "objective indicator" to start a DUI investigation.

The use of a PAS device is often challenged by DUI defense lawyers because the technology is not approved by the Illinois State police, there are unclear calibration standards, and detection of alcohol does not necessarily equal a reasonable suspicion of impairment. PAS devices are not part of Illinois' implied consent laws; no refusal penalties apply, and no statutory warnings are required. Even without legislation governing PAS devices, the technology must still pass constitutional scrutiny.  

Is the Use of a PAS Device Considered a "Search" Under the Fourth Amendment?

There are arguments for and against the question of whether a PAS device could reasonably be considered a "search" under Fourth Amendment guidelines. Arguments that contend the PAS is a search include:

• The PAS device enhances a police officer’s perception beyond his or her "natural" senses.
• The PAS device detects information that is not otherwise available without technology.
• There is no general public use for PAS devices.
• The PAS device targets the driver’s exhaled breath, which has at least some expectation of privacy.

Arguments that maintain a PAS device is not a search include:

• The device only measures environmental ethanol, not a person’s BAC level.
• Officers are already permitted to note the smell of alcohol coming from inside a vehicle.
• Detecting the odor of alcohol in public airspace should not be considered "private."

PAS Device Reliability Issues

The PAS only detects the presence of ethanol, meaning false positives can come from hand sanitizer, air fresheners, recent passengers who were consuming alcohol, or a spilled drink. With no mandatory calibration standards, PAS devices have inconsistent testing requirements. If a PAS device is used, it should be viewed the same as an officer saying "I thought I might have smelled alcohol," rather than scientific evidence.

PAS evidence can be challenged based on the officer failing to disclose the use of a PAS device, other legitimate environmental alcohol sources, or the absence of calibration logs. A defense attorney may also argue that there is no statutory authority to use a PAS device and that the device has questionable or unreliable performance. A PAS device can prolong a traffic stop without providing reasonable suspicion, and some would say the technological enhancement counts as a "search" under the Fourth Amendment.

Contact an Aurora, IL DUI Lawyer

If you were stopped for DUI and believe the officer used a PAS device to justify questioning or your arrest, your rights may have been violated. An experienced DuPage County, IL criminal defense attorney from the Law Office of Patricia Magaña, LLC can build a solid defense on your behalf while raising constitutional concerns. To schedule your free consultation, call 630-448-2001. Attorney speaks Spanish.