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What Is an Interlock Ignition Device and Should I Ask for One?



An ignition interlock device (IID) is a mechanism that is larger than a cell phone. It is wired to a car’s ignition system and installed in the dashboard. The IID functions in the same manner as a Breathalyzer: the driver breathes into the device and the mechanism records the driver’s blood alcohol content (BAC). The IID requires a driver to provide a breath sample in order to start the car's engine. If the device detects the presence of alcohol on a driver’s breath, the car will not start. The device also requires occasional breath samples from the driver throughout a trip to make sure alcohol is not present in the driver’s system on a continual basis. The legal limit of the percentage of alchohol in a driver’s system varies by state, according to legislation. However, most devices will only work if a driver’s BAC is .02 percent to .04 percent or below.  Both Tennesse and Oklahoma require interlocks for first time DUI-offenders.

How Are IIDs Installed?

The IID is easy to install by professionals, and the process can be completed while a driver waits. A driver that has been orderd by the court to have an IID installed is responsible for the payment of rental fees for the machine and installation fees. The mechanisms are supplied by private companies that rent the machines to drivers with approval of the court system and law enforcement. The devices cost several hundred dollars to install, and the monthly rental fee is about $70 to $100. Additional expenses for maintenance and calibration may apply.

Why Are IIDs Used?

Driving under the influence (DUI) of drugs and/or alcohol is a serious problem in the United States. In response to this crisis, states have legislated a variety of DUI penalties to reduce drunk driving, including jail sentences, criminal fines, suspension of the driver’s license privileges, or installation of an IID.

Many states order drivers to have IIDs installed in their cars as a consequence of a prior DUI conviction. A driver might also be ordered to have an IID installed on the first DUI conviction if the blood alcohol content (BAC) was over .15 percent; if the driver refused to take a chemical alcohol test during the stop; or if the driver caused injury to a passenger or pedestrian during the DUI offense. In some jurisdictions, drivers must have IIDs installed as a prerequisite to being allowed to drive again after their driver’s licenses are suspended as result of a DUI conviction. Some states use the IID as a form of punishment, penalty, and/or sanction to curb repeat DUI offenses by drivers who have been convicted for one or more DUIs.

Can an Offender Request an IID to Avoid or Reduce Penalties?

It is unlikely a driver can recommend installation of such a device to avoid probation, community service, and/or a jail sentence that may otherwise be associated with sentencing for a DUI conviction. The device is expensive, and its installation is a serious consequence intended to prevent loss of life from drunk driving. It is not the same as a speeder volunteering to take a driver’s education course to reduce points on a driving record or a fine.