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 Arizona, an alcohol ignition interlock device (IID) is mandated for all individuals convicted of DUI, including first-time offenders. The device prevents a vehicle from starting if the driver's BAC is above a preset limit, typically .02 BAC. Installation must be done by a state-approved technician, and the device records data for court monitoring purposes. Arizona law requires the use of IIDs for a specified period, which can vary based on the severity of the offense and the number of prior DUI convictions. For a first offense, the IID is generally required for at least 12 months. Subsequent offenses may result in longer periods of IID use. The court has the discretion to order the installation of an IID as a condition of bond or probation. Despite the effectiveness of IIDs in reducing repeat DUI offenses, there is a gap between those arrested for DUI and those who actually have an IID installed.