An ignition interlock device (IID) is a breath-testing unit wired into a car's ignition that will not let the engine start unless the driver blows a breath sample below a set alcohol threshold — and many states now require one after a DUI/DWI conviction, sometimes even for a first offense, either as a condition of getting your license back or as a condition of probation. Whether you need one, for how long, and what it costs depends entirely on your state's law and your specific case, so the details below are patterns to help you understand the system, not a substitute for checking your state's rules or talking to a lawyer.
What an Ignition Interlock Device Actually Is
An IID is a small breathalyzer mounted near the steering column and connected to the vehicle's starter circuit. Before the car will start, the driver blows into a mouthpiece. If the reading is at or above the programmed limit — typically a low threshold well under the state's legal driving limit — the car simply will not start. The device also requires "rolling retests" at random intervals while you're driving, so you can't just have a sober person start the car and then hand you the wheel.
Every test result, pass or fail, along with attempts to tamper with or bypass the unit, is logged and periodically downloaded by the installing service, which reports the data to the court, the department of motor vehicles, or your probation officer, depending on your state's system.
When Is an IID Required?
IID requirements come from two different tracks that often overlap:
Administrative/DMV track: Many states require an IID as a condition of restoring driving privileges after a DUI-related license suspension, separate from whatever happens in the criminal case.
Criminal/court track: A judge can order an IID as a condition of probation or as part of sentencing after a conviction.
A growing number of states impose interlock requirements even for a first-offense DUI, particularly if the blood alcohol concentration (BAC) was elevated, a minor was in the vehicle, or there was an accident involved. Other states only require interlocks for repeat offenders or for people whose license was suspended for refusing a chemical test. Because this varies so much by state — and because some states are moving toward interlock-only options that let first offenders drive immediately instead of serving a hard suspension — you need to check your own state's DMV and current statute (or ask your attorney) rather than assume how your state handles it.
How Long Do You Have to Keep One?
Interlock periods generally range from a few months to several years, and the length typically increases with prior offenses, BAC level, or whether the case involved injury. Some states also require a minimum period of consecutive "clean" driving (no violations) before you can remove the device, meaning a violation can restart the clock. Don't assume a specific number of months applies to you — the order from your court or DMV notice will state your specific requirement, and it's worth confirming that period hasn't changed if your case has been open for a while.
What It Costs
IIDs are typically installed and monitored by private vendors approved by the state, not by the court itself, and the driver is usually responsible for the cost. As a rough sense of scale:
An installation fee is charged when the device is put in the vehicle.
A recurring monthly monitoring/lease fee covers the device rental and data reporting.
Periodic calibration visits (often monthly) are required to keep the device certified and to download logged data.
A removal fee applies at the end of the required period.
Total costs commonly add up to a meaningful ongoing expense over the required period. Some states offer indigency waivers or reduced-fee programs for drivers who can't afford the cost — ask the vendor or the court clerk whether your state has one, since not all do and the process for applying varies.
Restricted or "Interlock" License Conditions
In many states, agreeing to install an IID is what allows you to get a restricted license instead of serving a full suspension with no driving at all. That restricted license usually only lets you drive vehicles equipped with the interlock, and it may still limit where or when you can drive (for example, to work, school, treatment, or medical appointments) depending on the type of restriction your state issues. Driving a non-interlock vehicle, or having someone else's un-equipped car, while you're subject to an interlock-restricted license is generally treated as a separate violation.
Lockouts and What Happens After a Violation
Two different things can stop you from driving:
A failed startup test usually just means the car won't start; you typically wait a short period and can retest.
A "lockout" is more serious — it happens after repeated failures, a missed calibration appointment, or signs of tampering, and it can disable the vehicle until you get it serviced by the vendor.
Violation data is reported to the court, probation, or the DMV, and a pattern of failed tests or tampering attempts can lead to an extended interlock period, a probation violation, or reinstated suspension. If you get a notice of a reported violation, don't ignore it — respond and get it addressed (through the vendor and, if needed, an attorney) before it turns into a bigger problem.
What to Do If You've Been Ordered to Install One
Get the exact order in writing — the court order or DMV notice will specify the device period, any restricted-license terms, and the deadline to install.
Confirm the deadline. Some states set a short window to install the device and provide proof to the court/DMV; missing it can mean an extended suspension with no driving at all.
Use a state-approved vendor. Courts and DMVs maintain lists of certified installers — using an unapproved device generally won't satisfy the order.
Ask about fee waivers before you pay if cost is a hardship.
Follow the calibration schedule exactly and never let anyone else blow into the device for you — that's typically treated as tampering or a circumvention attempt and can carry its own separate penalties.
Keep your own records of installation, calibration visits, and any disputed test results.
Talk to a defense attorney if you're unsure whether the requirement applies to you, if you think a violation was reported in error, or if the interlock condition is tied to a case that's still open.
Time-Sensitive Deadlines to Watch For
DUI cases usually run on two parallel clocks, and both move fast:
The DMV/administrative license clock — after an arrest, many states give you only a short window to request a hearing to contest an automatic license suspension. Missing that window can mean the suspension takes effect automatically, regardless of how the criminal case turns out.
The criminal case clock — arraignment dates, deadlines to request certain hearings, and any appeal deadline after sentencing are typically short and strictly enforced.
Because these windows are often measured in days, not weeks, and vary by state, check your arrest paperwork or DMV notice immediately for any stated deadline, and contact an attorney right away if you're not sure what applies.
Your Rights Still Apply
An interlock requirement is a consequence that follows a DUI arrest or conviction, but the underlying case is still a criminal matter where your constitutional rights apply in full. You are presumed innocent, and the prosecution — not you — has the burden of proving guilt beyond a reasonable doubt. You have the right to remain silent and the right to an attorney, including a court-appointed one if you cannot afford counsel (Gideon v. Wainwright, 1963). Statements made in response to custodial police questioning are subject to the warnings required by Miranda v. Arizona (1966). And the Supreme Court has held that police generally need a warrant (or your voluntary consent) to require a blood test in a DUI stop, though breath tests are treated differently (Birchfield v. North Dakota, 2016) — a distinction that can matter for how a case, and any resulting interlock order, unfolds.
Frequently Asked Questions
Can I get an interlock instead of losing my license entirely?
In many states, yes — installing an IID is often the trade-off that lets you keep some driving privileges instead of a full "hard" suspension. Whether that option exists, and its terms, depends on your state and the specifics of your case.
Does refusing the officer's breath test avoid an interlock requirement?
No. Refusing a chemical test typically triggers its own separate license suspension under your state's implied-consent law, and many states impose an interlock requirement specifically because of a refusal, independent of any DUI conviction.
What if the device gives a false positive?
Mouthwash, certain foods, and some medical conditions can occasionally trigger a false reading. Devices usually allow an immediate retest, and vendors log the data — if you believe a reported violation was a false positive, raise it with the vendor and the court promptly, ideally with an attorney's help.
Can someone else drive my interlock-equipped car?
Generally yes, other household members can drive the vehicle, but they'll need to blow into the device to start it and during rolling retests, which some people find inconvenient. Check your state's rules and the vendor's instructions.
This article is general legal information, not legal advice, and reading it does not create an attorney-client relationship. Ignition interlock rules vary significantly by state — confirm the requirements that apply to your case with your court, DMV, or a licensed defense attorney.
Frequently asked questions
Can I get an interlock instead of losing my license entirely?
In many states, yes — installing an IID is often the trade-off that lets you keep some driving privileges instead of a full suspension. Whether that option exists, and its terms, depends on your state and case.
Does refusing the breath test avoid an interlock requirement?
No. Refusal usually triggers its own license suspension under implied-consent law, and many states impose an interlock requirement specifically because of a refusal, separate from any DUI conviction.
What if the device gives a false positive?
Mouthwash, certain foods, and some medical conditions can occasionally trigger a false reading. Most devices allow an immediate retest; if a violation is reported, raise it with the vendor and court promptly, ideally with an attorney.
Can someone else drive my interlock-equipped car?
Generally yes, but they'll need to blow into the device to start it and during rolling retests. Check your state's rules and vendor instructions.
How long do I have to keep the device installed?
It ranges from a few months to several years depending on your state, prior offenses, and case facts, and some states require a minimum violation-free period before removal. Check your court or DMV order for your specific timeline.
This article is general legal information, not legal advice, and may not reflect the most current law or the law in your jurisdiction. Laws vary by state and change over time. For advice about your specific situation, consult a licensed attorney.
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