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 Indiana, the use of an alcohol ignition interlock device (IID) is governed by state laws that may require the installation of the device for individuals convicted of DUI/DWI offenses. The requirement to install an IID is typically determined by the court, and the device must be installed by a certified technician approved by the Indiana Bureau of Motor Vehicles (BMV). For first-time offenders, the court may order the installation of an IID at its discretion, while repeat offenders are more likely to be mandated to use the device. The IID prevents the vehicle from starting if the driver's BAC is above a court-set limit, commonly .02 BAC. The device records data such as breath test results and attempts to tamper with the device, and this information is reported to the monitoring company and potentially to the court. The duration for which an IID must be installed can range from one to three years or longer, depending on the court's orders. The installation of an IID may be a condition for bond or probation. Despite the effectiveness of IIDs in reducing repeat DUI/DWI offenses, a relatively small percentage of those arrested for such offenses end up with an IID installed.