U.S. state ignition interlock laws for alcohol impaired driving prevention: A 50 state survey and analysis

Objectives: Over the past two decades, all U.S. states have incorporated alcohol ignition interlock technology into sentencing laws for individuals convicted of driving while intoxicated (DWI). This article provides the first 50-state summary of these laws to include changes in the laws over time and their effective dates. This information is critical for policy makers to make informed decisions and for researchers to conduct quantitative evaluation of the laws. Methods: Standard legal research and legislative history techniques were used, including full-text searches in the Westlaw legal database and identification of state session laws. Because ignition interlock device (IID) laws often change over time, we identified the date of each law's initial enactment as well as the effective date of each law in its current form. Results: Beginning with California and Washington in 1987, all 50 states have enacted IID laws as a sentencing option for DWI offenders. Initially, most of these laws were discretionary. Today, however, 48 states mandate IID installation for at least some types of DWI offenders to maintain lawful driving privileges. Of these, 27 mandate an IID for all offenders; seven mandate an IID for repeat offenders only; and 21 for some combination of specific groups of DWI offenders, including repeat offenders, offenders with a blood alcohol content above a legislatively-specified level, and aggravated offenders (including those who harm someone else or who are convicted of a DWI with a child in the vehicle). Conclusion: States have wrestled with a number of IID policy issues, including for whom to mandate IIDs and whether to suspend a license for DWI prior to reinstating driving privileges with or without an IID. By understanding how state interlock laws differ, policy makers and researchers can ultimately better ascertain the impact of these laws.