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 Iowa, an alcohol ignition interlock device (IID) is a mechanism that prevents a vehicle from starting if the driver's breath alcohol concentration (BAC) is above a preset limit, typically .02 BAC. The Iowa Department of Transportation (DOT) oversees the certification of technicians who install IIDs. The device records data such as engine starts and stops, breath test results, and any tampering attempts, which is then reported to the monitoring company and potentially to the court. Iowa law mandates the installation of IIDs for all offenders convicted of operating while intoxicated (OWI), even for first-time offenders, if their BAC was .10 or higher, or if a minor was in the vehicle at the time of the offense. For repeat OWI offenders, IIDs are a mandatory requirement. The duration for which an IID must be installed varies based on the number of offenses and other factors, but it can range from six months to several years. The court may also require an IID as a condition for bond or probation. Despite the effectiveness of IIDs in reducing repeat DUI offenses, compliance rates are not as high as they could be, with a significant number of those arrested for DUI not having an IID installed.