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Can you trust a smartphone breathalyzer to tell you if are sober enough to drive?

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SALT LAKE CITY (KUTV) – With all the buzz about Utah’s recently changed DUI law, residents might looking for a way to know if they have crossed the .05 blood alcohol content threshold before you get behind the wheel.

There’s an array of ‘personal breathalyzers’ for sale that claim to show you your Blood Alcohol Content, so KUTV set out to see what Utah police think of these devices and if you can trust them.


We tested a popular personal breathalyzer against a court-admissible police breath test to see how the results compare, but before we get there, cops want to set the table for a discussion about drunk driving.

“The best option is that if you are going to drink, don’t drive,” Utah Highway Patrol Sgt. Nick Street told KUTV.

Street and other cops who spoke about personal breathalyzers were quick to point out that impairment begins at the first drink and there’s a lot more to DUIs than just a number on a breathalyzer.

“Troopers utilize preliminary breath testers to determine ‘positive’ or ‘negative’ for alcohol in one's body. And, it is just one of multiple tests used to determine if someone is under the influence of alcohol,” Street said.

The Dec. 2018 change to Utah DUI law lowered the ‘per se’ limit from .08 blood or breath alcohol concentration to .05, meaning if you blow above that limit, you’re getting a DUI. The statute, however, gives police the ability to issue a DUI regardless of BAC if they can prove impairment.

It's for that reason that UHP and other police agencies urge caution when using a personal breathalyzer.

“While there is a number shown on those devices, it doesn't necessarily speak to one's actual level of impairment,” Street said.


Last year, the Colorado Department of Transportation partnered with the personal breathalyzer company BacTrack to offer residents a 50-percent discount on their devices.

CDOT officials said they wanted to ‘normalize’ the act of checking your body’s alcohol content.

"Breathalyzers provide real-time data that helps people understand their blood-alcohol content so they can make informed decisions about driving," CDOT communications manager Sam Cole said in a news release to announce the partnership. “There is often a significant difference between how you feel and how impaired you actually are. Breathalyzers help eliminate that uncertainty, ultimately saving lives by removing impaired drivers from the road."

CDOT also handed out 475 BacTrack personal breathalyzers to first-time DUI offenders to avoid repeat DUIs.

BacTrack sells several different portable breathalyzers that go for around $100.

So between Colorado’s embrace of personal breathalyzers and Utah cops’ collective skepticism, we wanted to put the BacTrack to the test against the breath test that cops can take to court.


For our test, we got three volunteers who agreed to get a little tipsy in the presence of a police officer. Specifically, Cottonwood Heights Police officer Jake Griffith.

Our tests subjects, Kaleigh, Adiel, and James, had 50 minutes to consume alcohol from a selection that looked like a bad college party - beer, rum, cheap vodka, tequila, and a few pre-mixed cocktail drinks.

At the end of the 50 minutes, officer Griffith conducted a field sobriety test and waited the required 15 to 20 minutes to conduct an alcohol breath test. Each volunteer blew into the BacTrack, then a police Portable Breath Test (PBT) , and finally the Intoxilyzer.

The Intoxilyzer is basically the gold standard of breath alcohol tests and the results from it can be admitted into Utah courts.

Here’s what the respective tests said the breath-alcohol content was for each of our volunteers after 50 minutes of drinking:


BacTrack: .069

PBT: .060

Intoxilyzer: .058


BacTrack: .125

PBT: .116

Intoxilyzer: .124


BacTrack: .250

PBT: .260

Intoxilyzer: .240

The results were all very close and each volunteer would have been arrested for DUI if they had been behind the wheel of a car. We sent the volunteers home in an Uber or Lyft and then sat down with Officer Griffith to discuss the test.

“It would be a good tool to indicate whether yes, there is alcohol on board, or no there is not,” Griffith said. “I wouldn’t gauge it as saying ok, I just came under the legal limit so I’m good enough to drive, that’s not an indication because there’s many factors at play.”

Griffith has had a successful DUI conviction of a driver who blew a .03 on a breath test. He said the personal breathalyzer could be a good tool to determine if you still have alcohol in your system, but he echoed what the Utah Highway Patrol told us earlier about not driving after consuming alcohol.

“I would recommend still finding an Uber, getting a different ride, rather than taking a risk,” Griffith said.


So, big surprise, the cops don't want you to trust a personal breathalyzer to see if you are under the legal limit to drive and instead they recommend just to avoid driving after consuming alcohol altogether. But if you’re still not convinced, you should meet Stephen Letendre.

He teaches a state-required class to DUI offenders. You may have seen his bright yellow Toyota 4Runner driving around town with a giant red “.05” on it and his company logo,

“We have encountered students who have used [personal breathalyzers] thinking they were sober, trying to be responsible, and getting a DUI shortly thereafter,” Letendre said.

Letendre says not all personal breathalyzers are as accurate as the readings we found in our test with BackTrack and warns about a ‘false sense of security’ for drivers who use them.

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“Under .08 or .05 doesn’t mean you are sober,” Letendre said. “To say that this portable breathalyzer is telling me ‘yes,’ I have alcohol in my system’ I know there’s alcohol in my system, I don’t need to blow into a machine, and we say in our classes, ‘if you’ve had a drink, just don’t drive.”

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