Ignition Interlock Device FAQ

The ignition interlock device (IID) is installed in cars to prevent people from starting the vehicle if their blood alcohol content (BAC) is over a certain limit. While inventors developed them in the late 1960s, they became standardized in states around the country starting in the 1980s. Here are a few frequently asked questions about IIDs.

How Do IIDs Work?

An IID prevents an ignition signal from reaching the starter until the person breathing into the IID has a BAC under the device’s preprogrammed limit. For example, if the Texas Department of Public Safety (DPS) installed an IID into a person’s car, they may set the BAC at 0.04%. If a driver’s BAC is 0.05%, the vehicle will not start.

Who Pays for Them?

If you need an IID installed in your car, you will most likely pay for it yourself. They cost around $70–$150 to install and require periodic calibration, which can cost up to $60–$80 a month.

Are They Unconstitutional?

No, IIDs are constitutional. While IIDs may not seem fair, driving is a privilege and not a constitutional right. All 50 states have also passed laws allowing criminal courts to impose IIDs on drivers convicted of driving while intoxicated (DWI).

What Happens If I Don’t Install It?

In Texas, you have 30 days to install the IID. If you don’t install it by that time, your license will be revoked.

Where Do I Get It Installed?

The DPS has a list of certified locations near you where technicians can install the device. Check the DPS website for more information.

Will Mouthwash Trigger the IID?

Alcohol-based mouthwash can trigger the IID and result in a lockout. If you use mouthwash, make sure you use a product without alcohol or leave a cushion of time between using the rinse and blowing into the device.

Can the IID Be Tricked?

It’s tough to fool an IID. Developers predicted a number of methods people might use to get around the device, and they built it to counter these. Other individuals can use the device, but they would have to have a BAC lower than the specified amount, and they would have to ride in the car with you, as the IID will ask for periodic tests during the drive itself.

What Happens If I Fail the Breath Test?

If you fail the breath test, your car won’t start. The device will also place the vehicle in a temporary lock-out period for a few minutes after the first failed attempt. If you fail the test more than once, the waiting period for another test will be even longer.

If you’ve been ordered to install an IID in your automobile, or you face a DWI charge that could lead to the implementation of a device, you will need excellent legal representation. Contact one of our Dallas DWI defense lawyers to discuss your case.


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