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A motor cop’s guide to probable cause

Being aware of less obvious mechanical violations, in addition to the easier to recognize violations, will increase your knowledge and ability to contact


Consider common motor vehicle violations to establish probable cause.

Photo/Greg Friese

I understand not all of us are as excitable about the vehicle code as those of us in traffic enforcement, but I promise that having even a rudimentary knowledge base surrounding that rather a large book can come in quite handy when you’re looking for a good reason to stop and chat with a driver. I also understand that not all of us have a “Rain Man”-like Rolodex embedded in our respective psyches in which we store the aforementioned vehicle codes.

The key to it isn’t necessarily having a numbered section on the tip of one’s tongue to flaunt about when the soon-to-be suspect asks, “Why did you stop me?” If you can rattle off busted taillight that works just as well as saying CVC 24252(a).

My hope is to educate you on some common mechanical violations that are great for establishing probable cause or jumpstart your memory from the countless number of years ago in which you attended the police academy.

Before starting, I have to admit to a deficiency. I am fairly fluent in the California Vehicle Code, but I don’t know a thing about the Insert-Every-Other-State Vehicle Code. Consequently, you’ll have to take the plain text language from here and do a bit of research to find the specific sections to which I will be referring. I apologize in advance for my obvious shortcomings; however, I have faith in your ability to Google your state’s vehicle code.

Common motor vehicle violations

I’m not sure why the universe deemed it so, but more often than not, scofflaws drive dilapidated cars. Let’s start with some easy violations.

Vehicle lights

There’s the aforementioned broken taillight, but lighting sections can be incredibly helpful to know. Understandably, this applies more to you night owls than those of us on day shift, but imagine if vehicle lights are all supposed to be operational. That means the brake lights, headlights, reverse lights and even the license plate light need to work. If a light is out or even dim you have a stellar reason to chat up the driver.

If a broken taillight is covered with tape, even the same color tape as the light (nice try), that’s no good. Ground effect lighting looks tough in movies, right? Sure, but almost every second of “The Fast and the Furious” is jam-packed with illegal equipment. Those ridiculous lights on windshield wipers, rims and trim are all illegal.

Another great section to know, especially for you swing/grave-types, is driving without headlights. What’s your state’s code on low and high beam use?

Missing license plates

Another easy one (at least in California) is no front plate. It never ceases to amaze me how many cars I see with no front plate. Now, do I cite for it? Sometimes. By and large, it’s a good reason to see who is in the car, contact them and see if there is any criminal activity afoot.

Uncommon motor vehicle violations

Those are some easy examples to identify violations. Let’s talk about some uncommon violations.

Excessive exhaust and noise

If a car is smoking out the back end as it cruises through your response area or the exhaust is excessively loud, you have a violation.

Broken or obstructed windshield

Another violation you may see more often than you realize is the broken windshield. The key to that violation is that the defective condition of the windshield must impair the driver’s vision.

While the days of a pine-scented air freshener hanging from the rearview mirror as a good reason to stop someone have long passed us by, you’ve got to be able to articulate the violation’s inherent obstruction. Granted, if there are 40 air fresheners hanging there, that’s a whole different kettle of fish.

Vehicle is unsafe

Remember that scene in “Planes, Trains and Automobiles” where Steve Martin and John Candy get stopped in a burned out wreck of a car? The cop pulled them over because the vehicle was “unsafe.” It’s a pretty vague section, so if you can articulate why the vehicle is unsafe, you’re good to go.

Along those same lines is the condition of the vehicle’s tires. If there is less than 1/32” of tread depth, it’s a violation. Of course, most of us don’t carry a tread gauge, but if you wouldn’t drive with those tires, it may be worth a closer look. If you see metal instead of tread, you’ve got a violation.

Sadly, some of my greatest memories of childhood are now illegal. Riding in the back of my dad’s ’65 GMC pickup with my dog untethered in the bed are both violations. Sure, I see the ridiculous danger inherent in it, but it was fun while it lasted.

Speaking of hauling things around, if a vehicle is being used to haul just about anything that can fall out (think dump run in a pickup truck), the operator is required to cover the load to prevent spillage. Also, if you can’t see out the back using your rearview mirror, you must have both a left- and right-side mirror. If you can see out the back using your rearview mirror, then only a left-side mirror is required, but a vehicle must have a minimum of two mirrors (one being the left-side) at all times.

Being aware of less obvious mechanical violations, in addition to the violations that are easier to recognize, will increase your knowledge and ability to contact a citizen.

This article, originally published 9/12/2016, has been updated

Jason Hoschouer is a law enforcement officer with an agency in the San Francisco Bay area in California. In addition to patrolling the streets as a motor officer, Hoschouer helps fellow LEOs with financial coaching through his company, GPS Financial Coaching. Hoschouer’s column on Police1 covers everything from motors to monies, from britches to budgets. Jason has been blogging under the pseudonym “Motorcop” at since 2008 and was also a columnist for American COP Magazine for several years.

You can connect with him on Facebook and Twitter.

Contact Jason Hoschouer