Promising Sentencing Practice No. 5
Ignition Interlock Devices

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By Judge Calvin Holden (Missouri)

While DWI sanctions have generally focused on punishing, rehabilitating, or incapacitating the drinking driver, another approach to controlling the DWI offender that has emerged in recent years is to focus on the offender’s vehicle as a means of influencing the offender. One of these approaches, which has proven to be effective, is the ignition interlock device.

To prevent a convicted DWI offender from driving while intoxicated, courts may require the installation of an ignition interlock device on the offender’s vehicle. Courts employ this sentencing practice because:

  • Installation of the device allows DWI offenders to maintain their responsibilities (e.g., driving to work, taking children to school, running errands, etc.), while also serving as a constant reminder that their privilege to drive is contingent on their sobriety.

  • Given the fact that many offenders whose licenses are suspended or revoked will continue to drive without a license, a deterrent to DWI other than license suspension or revocation is necessary to protect public safety.


What Is An Ignition Interlock Driver?
An ignition interlock device consists of a breath-testing unit that is connected to a vehicle’s ignition switch. To start the vehicle, the driver must blow into the unit. If the breath sample provided by the driver contains more than a predetermined blood alcohol concentration, the ignition interlock device prevents the vehicle from being started. To meet the model specifications set by NHTSA, the ignition interlock device must not only require a breath test to start the vehicle, but must also require a subsequent “rolling or running retest” to prevent another person from starting the vehicle and then allowing an impaired driver to take over the wheel. The ignition interlock system records the results of all breath tests, as well as all attempts to circumvent or tamper with the device.

Federal Law
The TEA-21 Restoration Act supports the use of ignition interlock devices by mandating that State laws regarding second and subsequent convictions for DWI must require that all vehicles of repeat DWI offenders be impounded or immobilized for some time period during the license suspension period, or require the installation of an ignition interlock system on all of the offender’s vehicles for some time period after the end of the suspension. Otherwise, the State risks losing Federal funding.52


State Laws
Forty-three States have laws providing for either the discretionary or mandatory installation of ignition interlock devices on the vehicles of repeat DWI offenders. New Mexico, for example, requires that as a condition of probation upon a first conviction for aggravated driving while under the influence of intoxicating liquor or drugs,53 an offender shall be required to have an ignition interlock device installed and operating for a period of one year on all motor vehicles driven by the offender.54

The offender is required to pay for the ignition interlock device. The average cost for installation of the device is approximately $100-$150, and monthly monitoring and calibration is approximately $65.

Effectiveness Of The Device
The ignition interlock device has proved to be an effective deterrent to DWI because when properly installed and regularly monitored, the device is extremely difficult to circumvent. It has also proved to be an effective deterrent when it is emphasized to the offender that this is a lesser penalty than might be imposed (e.g., impounding the offender’s vehicle) and is conditioned on the offender’s correct use of the device every time he or she drives.

Studies have shown:

  • A recidivism rate of 0-4 percent by offenders whose vehicles were equipped with an ignition interlock device.55

  • That offenders were 65 percent less likely to re-offend while the device was in place than those offenders who were not required to install the device.56

  • That multiple DWI offenders who were required to install ignition interlock devices were less than half as likely to have subsequent DWI convictions within three years, as compared with other multiple DWI offenders who were not required to install the devices.57

  • That after 30 months, the recidivism rate for offenders placed in an interlock group was only 1.5 percent, compared to 16.1 percent for offenders in the non-interlock group.58

  • That a program which combined an ignition interlock requirement with substance abuse treatment and license suspension was more effective in preventing recidivism than any other program.59

Other researchers have found, however, that the deterrent effect of the device generally ends once it is removed, and that the likelihood that offenders who were required to install the device will commit a repeat DWI offense following removal of the device is virtually the same as for those who were not required to install the device.60 Research suggests that the device should remain installed until the offender can demonstrate an extended period of sobriety.61 When combined with substance abuse counseling, there is some evidence that the deterrent effect of the device may continue beyond its removal.62

One court found that the practical effectiveness of the device was limited because only a small number of offenders were willing to install the device in order to be able to drive legally. Consequently, it adopted a court policy that created a strong incentive for offenders to install the device by making traditional penalties, such as jail or electronically monitored house arrest, the alternative to participation in the interlock program. Comparison of the recidivism rates of offenders subject to this policy with offenders in similar, nearby courts, not using interlocks, indicated that the policy was producing substantial reductions in DWI recidivism.63


Using Data Recorded by Device
The data recorded by the ignition interlock device may provide information regarding the offender’s particular pattern of alcohol abuse that may be useful in attempting to change the offender’s behavior through counseling or other means (e.g., by showing the offender’s attempts to drive while intoxicated at a certain time of day or under certain circumstances).64 Some researchers have concluded that interlock data may eventually come to serve as a useful adjunct for monitoring offenders by alcohol counselors, as well as by courts and motor vehicle authorities.65

Barriers to Using the Device
Judges and prosecutors who participated in a 2003 study conducted by the California Department of Motor Vehicles noted three barriers that exist to requiring ignition interlock devices:

  • Many offenders are unable to pay for these devices;

  • Many offenders do not own a vehicle; and

  • Monitoring offenders ordered to install an ignition interlock device is time-consuming and difficult.66

One method of dealing with offenders who do not own a vehicle is to require them to sign a waiver stating that they will not own or operate a vehicle that
is not equipped with an ignition interlock device.

52 See 23 U.S.C. § 164(a)(5)(B).
53 N.M. Stat. §66-8-102 (D): Aggravated driving while under the influence of intoxicating liquor or drugs consists of a person who:
(1) has an alcohol concentration of sixteen one hundredths or more in his blood or breath while driving a vehicle within this state;
(2) has caused bodily injury to a human being as a result of the unlawful operation of a motor vehicle while driving under the influence of intoxicating liquor or drugs; or
(3) refused to submit to chemical testing, as provided for in the Implied Consent Act, and in the judgment of the court, based upon evidence of intoxication presented to the court, was under the influence of intoxicating liquor or drugs.
54 N.M. Stat. §66-8-102 (N).
55 See “The Technology Answer to the Persistent Drinking Driver,” National Commission against Drunk Driving (NCADD),
56 See Beck, Kenneth H., et al., “Effects of Alcohol Ignition Interlock License Restrictions on Multiple Alcohol Offenses: A Randomized Trial in Maryland,” American Journal of Public Health, Vol. 89, No. 11, pp. 1696-1700 (November 1999); Coben, Jeffrey, and Gregory Larkin, “Effectiveness of Ignition Interlock Devices in Reducing Drunk Driving Recidivism,” American Journal of Preventive Medicine, Vol. 16, No. 1S, pp. 81-87 (1999).
57 See Fulkerson, Andrew, “Blow and Go: The Breath-Analyzed Ignition Interlock Device as a Technological Response to DWI,” American Journal of Drug and Alcohol Abuse,” Vol. 29, pp. 219-229 (2003).
58 See More, Barbara J. and Delbert S. Elliott, “Effects of Ignition Interlock Devices on DUI Recidivism: Findings from a Longitudinal Study in Hamilton County, Ohio,” Crime & Delinquency, Vol. 38, pp. 131-141 (1992).
59 See Tashima, Helen N. and Clifford J. Helander, “1999 Annual Report of the California DUI Management Information System,” California Department of Motor Vehicles, pp. 30, 38 (January 1999).
60 See Raub, R., et al., “Breath Alcohol Ignition Interlock Devices: Controlling the Recidivist,” Traffic Injury Prevention, Vol. 4, No. 3, pp. 199-205 (2003); “Alcohol Ignition Interlock Devices I: Position Paper,” International Council on Alcohol, Drugs and Traffic Safety (ICADTS), p. 11 (July 2001).
61 See Raub, supra.
62 See Raub, supra.
63 See Voas, Robert A., et al., “Evaluation of a Program to Motivate Impaired Driving Offenders to Install Ignition Interlocks,” Accident Analysis and Prevention, Vol. 34, No. 4, pp. 449-455 (2002).
64 See Marques, Paul R., et al., “Predicting Repeat DUI Offenses With Alcohol Interlock Recorder,” Accident Analysis and Prevention, Vol. 33, No. 5, pp. 609-619 (2001); Marques, Paul R., et al., “Behavioral Monitoring of DUI Offenders with Alcohol Ignition Interlock Recorder,” Addiction, Vol. 94, No. 12, pp. 1861-1870 (1999).
65 See Marques, Paul R., et al., “Behavioral Measures of Drinking: Patterns from the Alcohol Interlock Record,” Addiction, Vol. 98, No. 2, pp. 13-19 (2003).
66 See DeYoung, David, “An Evaluation of the Implementation of Ignition Interlock in California,” Licensing Operations Division, Research Notes—2003,