An interlock device is installed in a motor vehicle to prevent a driver from operating the vehicle if the driver has been drinking. Before the driver can start the vehicle, the driver must blow into the device.  If the device detects a certain level of alcohol, it will not allow the car to start.

Interlock devices have been used in the United States for more than 20 years. All States have some legislation requiring or permitting the use of breath alcohol ignition devices, or “interlocks.”  

Interlocks are comprised of a breath alcohol sensor, a tamper-proof system, a data-recording system that logs results, and a retest system that is supposed to require the driver to provide another breath sample a varying time interval.

The primary purpose of the interlock devices is to prevent someone who has been drinking from starting or driving the car.  If the driver gives an alcohol-free sample of his breath and it is verified by the system, the device will provide power to the vehicle. The software in the system logs the test results and records other data, such as the number of times the car is turned off and on, mileage, etc.

Who has to have an Interlock Installed?

In Texas, the courts mandate an interlock device for certain charges.  In Tarrant County, most courts require interlocks during the pre-trial phase of a DWI charge if it is a second offense, an offense with a BAC above .15, an Intoxication Assault, or an Intoxication Manslaughter charge.  Some courts will also require an interlock as a condition of probation or as a condition of an occupational license (if your license has been suspended). For many of my clients, the fear and embarrassment of having an interlock required on your vehicle is one of their greatest concerns. I will do everything possible to help you avoid that requirement. 

How Long Does it Take to have an Interlock Installed?

Generally, interlocks can be installed in about an hour.

Who Pays to have an Interlock Device Installed on my Car?

If you are being required by the court to have an interlock on your car, you are responsible for the cost to install and maintain the interlock.

Someone Else is going to Drive my Car. How do they Start the Car?

Anyone using a vehicle with an interlock must blow into the device for the vehicle to start.  Most interlocks are now also equipped with a camera to verify who is driving.

Is the Use of Interlocks Common?

Yes.  In 2011, there were approximately 85,000 DWI arrests in Texas.  In 2012, there were over 37,000 interlocks in use.

It is extremely important to hire a knowledgeable DWI attorney if you are facing charges. Tarrant County Criminal Defense Attorney Stephen Handy represents individuals being accused of DWI and other criminal offenses.  Stephen is a member of the NATIONAL COLLEGE OF DUI DEFENSE and strives to be a leader in DWI defense

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