Ignition Interlock Device (IID)

In a few different situations, the DMV may require that you install an ignition interlock device (IID) on the vehicle(s) that you driver. This might be the case if you are convicted of a DUI or if your license is suspended related to a DUI stop. Learn more about the IID on this page.


Under Connecticut law, installation and use of an ignition interlock device is required in some situations. You must use this device before your driver’s license can be restored after an alcohol-related suspension. You need to use this device if:

  • You refused to take the breathalyzer test.
  • You lost your driver’s license suspension hearing at the DMV.
  • You have been convicted at court of DUI.
  • You have been convicted of either vehicular manslaughter or vehicular assault.

If you fit one of these situations, you need to use the ignition interlock device in your car.

What is the Ignition Interlock Device?

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Ignition interlocks require the driver to provide an alcohol-free breath sample prior to starting their car, and again at random intervals while operating their car. Ignition interlocks are another consequence of your DUI.

An ignition interlock device (or “IID” for short) is a mini-breathalyzer that is installed in your car. It works just like the breathalyzer at the police stations. The IID is hardwired into your car’s battery by an approved vendor. Don’t worry, having the IID installed does not permanently harm your car. In addition to being able to control whether your car engine starts, the ignition interlock device contains a computer chip – similar to the “black box” in an airplane – that records every time that you test and logs data from every test result. The computer chip will also monitor if the IID has been tampered with.

In order to start your car and drive around, you will need to blow into the IID. The device will analyze your breath to check your blood alcohol content (BAC). Any BAC reading above the limit of the machine, and your car engine won’t start. The IID’s sensors are set to detect alcohol at very small limits. Even one alcoholic beverage is sufficient to trip the IID and disable your car’s engine from starting. The ignition interlock device does not do any permanent harm to your car’s engine. If it detects alcohol, it only temporarily disables the engine from starting for a certain amount of time. Any failed test will result in a violation.

In case you are wondering, you will have to pay for the installation and monthly maintenance of the IID, as well as all associated DMV costs. Again, another consequence of your DUI.

If you are a first offender, and you resolved your court case through a diversionary program, but lost your DMV hearing, then you are required to use the IID for six months. If you refused the police breathalyzer test, or if you were convicted of DUI in court, then you must use the IID for one year. Subsequent DUI arrests and convictions will increase the time you must use the IID.

Rolling Tests

You will also be required to provide “rolling” re-tests during operation. These re-tests take place at random times when you are driving your car. Rolling re-tests typically occur anywhere from five minutes to thirty minutes after the car has been started. The purpose of the rolling re-tests is to prevent you from drinking alcohol while you are driving, or from having a sober friend blow into the ignition interlock device to get the car started when you are under the influence.

If you don’t respond to the rolling re-test, or if the IID detects alcohol on your breath, the IID will trip some kind of warning. The warning varies from having your car’s headlights continuously blinking to having your horn honk until you stop the car and turn off the engine. The device WILL NOT just shut down your engine once your car has been started for obvious safety reasons. Missing a rolling re-test, or failing the rolling re-test, will result in a violation.


The IID needs to be serviced and recalibrated every month. The vendor will provide detailed information about this requirement. If you fail to get your IID serviced and recalibrated, the machine will lock you out, and you will require the assistance of the vendor to unlock the IID. Your car will not start and will need to be towed to the vendor’s service center, at your cost. Also, any lock out is considered a violation.

During the monthly maintenance, or after any lockout, the vendor will download your test data from the IIDs computer chip and generate a report on your operation. This report will be shared with the DMV and the prosecutor.

The report will indicate how many times you passed or failed the BAC test, as well as if you passed or failed rolling re-tests. Depending upon your test results, you face penalties of additional time requirements for the IID. The typical is 30 days additional per violation. In a worst-case scenario, the prosecutor could consider IID violations as transgressions against either the a diversionary program or your probation (if already convicted), and have your case restored to the court’s docket for further prosecution.


If you are required to have an IID, and you are caught driving without an IID by the police, they will arrest you and they will charge you with an additional crime. This misdemeanor crime carries penalties of up to one year in jail, 30 days of which are mandatory, a fine of not less than $500 nor more than $1,000, and an additional driver’s license suspension period with extended IID requirements.

Anyone caught trying to bypass or tamper with the IID to start their vehicle will also be charged with an additional crime. This is a Class C misdemeanor which carries up to 90 days in jail and $500 fine. In addition, you will lose your driver’s license for one year.

Getting Help

My office provides all of my DUI clients with detailed information about the installation of IIDs, including vendor recommendations, and instructions to navigate the required DMV forms. If you have specific questions about IIDs, please give me a call. I am here to help!

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