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 Mississippi, the use of an alcohol ignition interlock device (IID) is regulated under state law as a measure to prevent repeat offenses of driving under the influence (DUI) or driving while intoxicated (DWI). The state mandates the installation of IIDs for all individuals convicted of a second DUI offense within a five-year period, as per Mississippi Code Section 63-11-30. For first-time offenders, the court has the discretion to order the installation of an IID as a condition of reinstating driving privileges. The device must be installed by a certified technician approved by the Mississippi Department of Public Safety. The IID prevents the vehicle from starting if the driver's BAC is above the preset limit, typically .02 BAC. The data collected by the IID, including breath test results and any tampering attempts, is reported to the monitoring company and then to the court. The duration for which an IID must be installed can vary, but it is often required for a period of 1 to 3 years, depending on the severity of the offense and the court's decision. Despite the effectiveness of IIDs in reducing repeat DUI/DWI offenses, there is a noted gap between the number of individuals arrested for such offenses and those who actually have an IID installed.