An alcohol ignition interlock device (IID) is a breath-test device that is connected to a vehicle’s ignition. A vehicle with an IID installed will not start unless the driver blows into the interlock and has a blood alcohol concentration (BAC) below a limit set by the court—usually .02 BAC. IIDs must be installed by a certified technician approved by the state’s department of motor vehicles (DMV). The IID will collect data (engine starts and stops, breath test results, and tampering attempts) and report it to the monitoring company, which will report it to the court.

IIDs reduce repeat offenses for DUI/DWI by approximately 70% when installed. Laws vary from state to state and courts have significant discretion, but a judge may order a person convicted of a first DUI/DWI offense to install an IID and will order a person convicted of a second or third DUI/DWI to install an IID. Courts will often order an IID installed on the defendant’s vehicle as a condition of bond (to be released from jail) and of probation (following jail or prison time, or in lieu of any or more jail or prison time). The court may order the defendant’s IID to remain on the vehicle for 1-3 years or more.

Despite these laws and programs, only about one-fifth of those arrested for DUI/DWI have an IID installed.

In Minnesota, an alcohol ignition interlock device (IID) is a mechanism used as a preventive measure for individuals convicted of DUI/DWI offenses. The state's program mandates that drivers with a BAC above the legal limit of .08, or those who refuse a breath test, may have to use an IID to retain their driving privileges. The device prevents the vehicle from starting if the driver's BAC exceeds .02. First-time offenders may be required to install an IID at the court's discretion, while repeat offenders are typically mandated to use the device. Installation must be performed by a state-approved technician, and the device records data for monitoring purposes. The duration for which an IID must be installed can range from one year to several years, depending on the severity of the offense and the court's orders. Despite the effectiveness of IIDs in reducing repeat DUI/DWI incidents, a significant number of those arrested for such offenses do not end up with an IID installed.