Can a Laser Give Me a DUI?

Laser GunCan a laser give me a DUI? Someday, perhaps. A new remote sensing device uses lasers to detect the presence of alcohol vapor in a moving vehicle. In the future, law enforcement officers could use potentially use this device to “pre-screen” cars that they want to stop for suspected DUIs. The device, developed by scientists at the Military University of Technology in Warsaw, Poland, is set up to sit by the side of the road and monitor each passing car. If alcohol vapors are detected in a car, the device sends a photo of the car with its license plate number to a law enforcement officer waiting by the road farther down. The officer then stops the driver and determines if he or she is sober.

The device uses four laser beams, merged into one with a special mirror. The beams are broken up into pulses to synchronize detection. The first beam has a wide absorption band, which allows the laser to see the ethyl alcohol in the air. The second beam is thinner, and allows the laser to differentiate the alcohol from water. The third beam helps the laser see through windows that are not all the same thickness. The fourth beam is in the visible spectrum and allows the device to actually see what it is doing. The device uses a mirror on the opposite side of the road to reflect the beam back to the detector. The reflection gives the beam a second look at the air and increases accuracy. The device is capable of detecting a driver with a blood alcohol concentration (BAC) of 0.01%. In California, the BAC of an adult must be below 0.08%.

There are multiple problems with the device. It cannot determine the source of the alcohol vapor. This means the device does not know who is drunk: the driver, the passengers, or both. The device may also not be able to detect if the alcohol vapor is coming from spilled alcohol. Alcohol vapor could also be coming from perfume, mouthwash, or other substances. The device cannot detect the vapor if the car’s windows are tinted, are rolled down, or there are solar screens on the side windows. As to these last factors, however, an officer, can see if the measures are being employed. Then the officer can determine whether they want to stop the car.

The legislation that protects drivers against the “search” by this device, and the subsequent possible search and seizure by law enforcement officers, is the 4th Amendment to the U.S. Constitution. There are also protections under state law in provisions that regard a person’s rights to privacy and to be free from unreasonable searches and seizures. In the California Constitution, these protections would be afforded by Article 1, Section 1 (right to privacy) and Article 1, Section 13 (right to be free from unreasonable searches and seizures).

In California, officers need reasonable suspicion that the driver is drunk to stop a car for a DUI. They can also legally stop a car for a traffic violation. The information provided by the device is unlikely to give an officer reasonable suspicion that the driver of the vehicle is drunk. The device cannot pinpoint the driver as the source of the alcohol vapor, and confirm that the driver has been drinking alcohol. This means that a court would be unlikely to determine that it was legal for officers to stop a car after “searching” it with this device.

It should be noted that there are also problems with the technology with which the device can be partnered. Cameras do not always take accurate pictures of license plates. Also, officers sometimes use automatic license plate readers (APLRs) instead of cameras. APLRs often read license plates incorrectly. This has led to the wrong cars being stopped. As of June 2014, in general, Sonoma County does not use APLRs. The exception is the Petaluma Police Department, which uses APLRs for parking enforcement. A number of police departments in cities in the East Bay and Marin County, including San Rafael and Novato, use APLRs. The California Highway Patrol also uses these devices. Napa County just concluded a year-long study of traffic behavior in which it used cameras, set up at 12 locations in and around the county, to capture images of license plates.


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