Ignition Interlock Requirements in California

Virginia Landry and Team

What Is an Ignition Interlock Device?

As a California resident, you may have heard about or even seen Ignition Interlock Devices, otherwise known as IIDs. They are small cellphone-sized devices that are hooked up to a car’s steering column. They are basically small breathalyzer machines that require a driver to provide alcohol-free breath samples before a vehicle can start. 

They also require the driver to provide random breath samples throughout their trip. This is to prevent someone else from blowing into the device on behalf of the driver, and then the driver getting into the car to drive away.  

As more and more states are attempting to crack down on drunk driving, they are utilizing these devices as just one of the DUI penalties a convicted drunk driver can be subjected to.

How Does an Ignition Interlock Device Work?

Every time a driver blows into the device, a log will be kept of the results. If the driver blows a BAC that is above the legal limit, the car will not start. 

This log is sent to the police department.  If the log indicates that a driver blew above a certain percentage (a percentage pre-determined by the judge or prosecutor, usually .03 or .04 percent or more) the police and prosecution have the right to seek additional penalties.

If a driver provides a clean breath sample when they start the vehicle but they later have alcohol in their breath, the car won’t automatically shut off because this could endanger the driver and put lives at risk. Instead, the breath sample will be recorded and the information will be sent to the court.

If you are convicted of DUI and the court orders you to install an IID, you must have it installed by a court-approved installer and you must have one installed in each vehicle you drive for personal use.


You may be wondering, “Can my passenger blow into the device for me if they haven’t been drinking?” No, not only is this illegal, but the IIDs are designed not to reach across to the passenger side of the vehicle. If you asked someone else to do this for you, they would be committing a crime under California law.

When are DUI defendants required to install an IID? It depends on the facts of the case, but IIDs can be ordered in any type of DUI-related offense that occurs in California. You could be ordered to install an IID if you are convicted of:

  • Driving under the influence under Sec. 23152(a) of the California Vehicle Code.
  • DUI with a BAC of 0.08% or greater under Sec. 23152(b) of the California Vehicle Code.
  • DUI causing bodily injuries.
  • Driving on a suspended or revoked license after a DUI conviction.

Should someone attempt to dismantle the interlock device, this attempt will be recorded electronically on the device's memory.

Related: California DUI Basics

When Is an IID Required?

As a general rule, a California judge can order a defendant to install an IID for up to three years whenever the judge thinks it’s necessary. However, judges don’t usually order IIDs for first DUIs unless the defendant’s blood alcohol concentration (BAC) was 0.15% or more, or the defendant refused to submit to a blood or breath test.

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