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 Washington State, the use of an alcohol ignition interlock device (IID) is mandated by law for individuals convicted of driving under the influence (DUI) or driving while intoxicated (DWI). The Washington State Department of Licensing (DOL) oversees the IID program, which requires drivers with a DUI conviction to install an IID on all vehicles they operate. The device prevents the vehicle from starting if the driver's breath alcohol concentration (BAC) is above a preset limit, typically .02 BAC. First-time offenders may be required to install an IID at the discretion of the court, while repeat offenders are generally mandated to use the device. Installation must be performed by a state-certified technician, and the device records data such as engine starts, stops, breath test results, and any tampering attempts, which is reported to the monitoring company and then to the court. The duration for which an IID must be installed can range from 1 to 3 years or more, depending on the severity of the offense and the court's orders. Despite the effectiveness of IIDs in reducing repeat DUI/DWI offenses, compliance rates are not as high as the law intends, with only a fraction of those arrested for DUI/DWI actually installing an IID.