Recent changes in the law ushered in a statewide use of interlock devices.

Interlock laws in California are not new.  They existed for many years in four “pilot counties,” Alameda, Tulare, Los Angeles and Sacramento Counties.  However, the previous interlock law and the new one have important differences, one of which is that for first offenders, the interlock device in the new law is NOT mandatory.

Now that you may be subject to it, what should you do?

Do not install the interlock device right away. It should be your LAST and not FIRST option.

Because the interlock device law is NOT mandatory for first offense DUIs, those persons charged with first offense DUIs MUST be aware of the options available.  The interlock device should be used as a LAST OPTION in a first offense DUI and not as the first one.  It can be avoided.

Why should it be the last option and how can it be avoided?

Before we can discuss that, you must have a better idea of what an interlock device actually is and what the new law is about.

TWO notes of caution.  First, many persons in positions of authority, including law enforcement, prosecutors and even judges, may misinterpret this key fact that the interlock device for first offenders is OPTIONAL. Second, you may be subject to a barrage of misleading and intimidating advertising, including phone calls, from less than reputable interlock companies and/or insurance companies, trying to capitalize on your uncertainty and vulnerability.  Some unscrupulous and/or misinformed persons may present information to you that the interlock device is required and that you should install it now because you will have to have it anyway.  This is patently wrong.  For first offense DUIs, the interlock is OPTIONAL.

How does an interlock device work?

To start a vehicle, once the interlock device is installed, a driver must blow into the device.  The device is designed to detect the presence of alcohol and disable the vehicle from starting if alcohol is detected.

The device also requires that periodically, while the vehicle is being operated, that the driver randomly must blow into the device.  This is called “rolling tests”.  This means, if the driver is operating the vehicle for a certain period of time, the device will randomly require the driver to blow into it.  IF the driver fails to provide the breath sample during the “window of opportunity”, the device will cause the vehicle’s lights to flash on and off and the horn to start beeping, much like if a car burglar has triggered a car alarm in the middle of the night. The device may need to be “reset” as a result of the driver’s failure to provide a sample.  The driver may have to pay for this “service.”

So, what about the interlock device itself?  What is a driver “getting himself or herself involved with” by having an interlock device installed?

The DMV surveyed first offender drivers who had used an interlock device and inquired whether they experienced problems with it.

53% reported problems with the interlock device.

41% of those reporting problems said the interlock device was UNRELIABLE.

20.7% of those reporting problems said the interlock device GAVE FALSE READINGS with food/drink.

10.3% complained that the interlock device DRAINED THEIR BATTERY.

10.3% reported that the interlock device MADE DRIVING DANGEROUS.

6.9% complained about SERVICING the interlock.

6.8% reported problems STARTING THEIR VEHICLES.

3.5% accused the installer of DAMAGING THEIR VEHICLE.

By far, the most common response is that the IID is unreliable. Some respondents simply said that the device is unpredictable/unreliable, while others said that it would shut down or lock up

10.3% of the respondents said that the interlock device makes driving dangerous. Some said that they almost became involved in a crash due to the IID, primarily because of the rolling retest.

“Another question on the survey specifically asked respondents whether they thought that IIDs interfered with their ability to drive safely. Approximately 37% said that their ability to drive safely was compromised by the IID. This is high enough to be of concern, and the question of safety deserves further attention. “

Survey information and quote from AN EVALUATION OF THE IMPLEMENTATION OF IGNITION INTERLOCK IN CALIFORNIA, by David J. DeYoung Research and Development Branch Licensing Operations Division © California Department of Motor Vehicles, 2002 California Department of Motor Vehicles.

The device can be expensive.  There is a monthly service fee. In addition, there may be installation fees.  There is a “calibration” service fee due every 60 days when the device is “calibrated.” Additional charges for service due to lockouts (true or false positive) may be applicable. There may be fees associated with any failures – including not registering a rolling test in time. There may be a “removal” fee.  The driver/user is responsible for any perceived damage to the device.


The interlock device can produce false readings that can cause you to be “locked out”/unable to use the device and therefore unable to drive your vehicle.

The false readings can cause a driver to lose money, because the interlock companies may charge to “unfreeze” the locked system.  The false readings can also potentially result in the court and/or Department of Motor Vehicle being notified and ultimately your license can be lost and suspended for the remaining time that it was to be restricted.  Your probation, if you were convicted of a DUI, could be “violated,” meaning that you could be subject to additional potential punishment, including incarceration, a longer period of interlock use (a judge could modify probation if violated to mandate that the interlock device be used for longer than the MINIMUM period of time required) and/or the actual denial by a judge of a restricted license.  The interlock device law allows a judge to deny a restricted license to a driver and instead suspend the driver’s license.

False positives have been reported to have been caused by various substances including baked or spicy foods.

Cumbersome or difficult operation due to different blowing techniques, rolling tests, and machine operation can lead to timely and costly consequences.


The technique to blow into the device may not be easy for some to do.  If you took a breath test either by the roadside and/or after arrest, do you remember any problems you experienced with either or both tests?  There is a technique to “blow” called the “hum and blow” technique, that some interlock device providers use to explain to their customers as to how to use the equipment.


You, the driver, are responsible for anyone that drives your vehicle. If another person borrows your car and registers a failure – any failed IID test is attributed to the person with the ignition interlock device requirement until proven otherwise. This includes potential false failures due to incorrect operation – including rolling tests

Regular car services can be interrupted. Allowing a non-approved mechanic to service your vehicle could result in a tampering violation resulting in a marked failure. This means regular servicing of your vehicle will be much more inconvenient and potentially more expensive. IID devices rely on your car battery for operation. This means extended wear and usage of your battery.


You can be “locked out” by the device. An IID that is having trouble accurately registering a test or may be having difficulty starting in inclement weather can cause lock out of vehicle resulting in towing to reset and ride service to get to work


Your privacy may be at risk. Many IIDs now come with cameras attached as a means of verifying user identity. A report submitted to details a customer’s experience where, during an IID service, customer noticed the camera was facing down at her legs and the mechanic was able to access all the pictures (Jordan of shoreline April 3 2018).


Interlock companies, and not the state, make the rules. Interlock companies have little governmental regulation and oversight.  Light governmental supervision could lead to engineering shortcuts that cause unnecessary and potential costly equipment error.   Interlock tests are handled exclusively by the companies (they benefit if you fail and have to extend use of IID).


What does the new law say?

Let’s get a glimpse of what the new law offers.  This article and its information in it, is NOT intended to supersede actual legal advice from an attorney nor provide it. It is offered only as a guide to open a discussion about what a driver’s choices are so that the driver makes the best decision for him or her.

The interlock device law offers the driver arrested for a DUI the immediate option of installing the device and getting a “restricted license”.  What does that mean?  “Restricted” here means that the driver can only drive a vehicle equipped with a functioning interlock device for the period time proscribed by the law.  So long as the driver has a functioning interlock device in any vehicle the driver operates, the driver can drive anywhere.

Many questions ensue, such as what if the driver also has to drive a vehicle owed by the driver’s employer or a rental car.   It is clear that for rental cars, the vehicle must also have an interlock device.  As for an employer’s vehicle, there is a statutory exception to allow a driver to be exempt from using an interlock device if the driver’s employer is aware of the DUI and signs a document for the DMV.   However, many persons are reluctant to inform their employers about a DUI because of the potential adverse employment consequences that may ensue.

When a driver is arrested for a suspected DUI, police are authorized by law to seize the hardcopy California license if they believe that the driver’s BAC was .08% or more at the time of driving.  This seizure constitutes a “taking” by the state of your privilege to drive; you are afforded “due process” to contest this taking via a DMV administrative hearing.

I believe that a driver whose license is seized pursuant to the DUI laws almost ALWAYS request a DMV hearing.   There are certain small exceptions when the driver should not, but those should be discussed with an attorney.  In virtually every case, a driver should request a hearing.


Three reasons at least.

First, the driver can keep his or her full privileges intact by requesting a hearing.

Second, the hearing process affords the driver the opportunity before going to court to obtain the “discovery,” a copy of the police report and chemical test results, and other important documents that the driver would normally get only much later, after first going to court.  Many persons harbor the mistaken idea that they can simply call police and get their police report and test results from the arresting agency.  This is incorrect and actually also potentially dangerous to the accused, because an accused should never speak with police about the underlying case.  An accused can make or be accused of making a statement that can and will be used against the accused in court.

I am mentioning all the above because it is UNCLEAR from this new law that if a driver opts to request an immediate interlock device he or she FOREGOES being able to request a DMV hearing to contest the potential loss of license.   Only time will tell how DMV and courts interpret this portion of the law.

But the point also is, why would you want to put on an interlock device and then, if you win your hearing, take it off?  It would seem far more logical, as was initially mentioned, to WAIT and use the interlock device ONLY as a final option in a first offense DUI case.   You do not “lose” the interlock option if you do not exercise it initially.

Exercising the option initially seems to be more problematic than if you do not.  For example, what happens if you put the device on your car immediately but your court case is not over quickly?  How long do you keep it on?  Wil the DMV send you a letter saying you can take it off?  And what happens if, after you have it on for the initial period of time and remove it, you are convicted in court of a DUI and have to put it on again?  Moreover, what prevents a judge from ordering you, once he or she sees you already have the interlock device installed, to keep it for MORE than the minimum period of time proscribed by law?  A judge can, as part of your probation, if warranted by the facts, do that.

For these and many other reasons, the reader is cautioned to NOT put the interlock device on immediately but instead reserve the decision and treat it as your final option.

Third, under the new law, the driver by installing the interlock device avoids the dreaded 30 day “hard suspension,” the minimum period of time during which a driver may not drive at all IF the driver either fails to request a DMV hearing OR loses the DMV hearing that he or she requests.  HOWEVER, under the prior “pilot” interlock law, drivers could and did avoid the 30 day “hard” suspension even IF they lost their DMV hearing by structuring their case procedurally in the correct manner.  I believe at this point in time, we must push the DMV to continue to use this interpretation as they previously did.  They may or may not.  BUT, again, the driver does NOT lose the option of ultimately installing the interlock device IF the 30 day “hard suspension” cannot be avoided.  This is one of the many reasons why a driver should consult with an experienced DUI attorney about what to do.

What happens at court if a person is convicted of a first offense DUI?

The driver has OPTIONS.  When a person is convicted of a first offense DUI, the court notifies the DMV.  The DMV then issues a letter suspending the driver’s license for six months.

The driver can either install the interlock device for six months AND receive an immediate restricted license (the driver must also be enrolled in the first offender DUI class, have an SR22 on file and pay a reissuance fee) OR the driver can decline to install the interlock device AND receive an immediate restricted license (the driver must also be enrolled in the first offender DUI class, have an SR22 on file and pay a reissuance fee).

What are the differences, if any, between the two options?  Duration of the restricted license and scope of the restricted license.

If a driver installs an interlock device, the restricted license is for six months and the scope, or driving that is permitted, is unlimited, meaning that the driver can drive anywhere so long as he or she has a functioning interlock device in any vehicle that he or she operates.  This includes employer’s vehicles and rental cars.   There is an exemption for an employer’s vehicle IF the driver discloses the DUI to his/her employer who signs paperwork and submits it to the DMV.

If a driver does NOT install an interlock device but is otherwise eligible for a restricted license, the restricted license is for twelve months and the scope, or driving that is permitted, is limited to driving to and from work and during the course of employment (meaning: driving for employment purposes, to visit clients, attend meetings/employment related functions such as dinners) and to and from the DUI class.  There are some “gray”/uncertain areas, such as if you are “employed” informally to drive a family member to any from appointments or if you need gas (of course permitted to drive to a gas station) and there is a food store at the gas station (e.g. Safeway or Costco), can you shop?  These issues should be addressed by a thorough discussion with an attorney.

BIG POINT: IF a driver opts to NOT install an interlock device initially and instead at some point during the 12 month restricted period decides that he/she should have one, the law allows the driver to install the interlock device.  The driver would then be required to use the interlock device for six months and would not receive “credit” for the period of time having driven under the restricted period without the interlock device.  BUT, it is unclear if the driver, once he/she has an interlock device installed, can decide to remove it and opt for the 12 month period of restricted driving described above.   Again, for this reason and many others, a driver should be very caution about rushing into an interlock installation.

Given all the above, I recommend (1) that the first time offender DOES NOT immediately install an interlock device and (2) proceeds with EXTREME CAUTION in opting for an interlock device.  The interlock device should only be used in the vast majority of first offense DUI cases as the FINAL option, and not the first choice.  The reader is again cautioned to discuss the reader’s particular facts and circumstances with a qualified DUI attorney to determine what the reader should do.