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Jim Wagner

The Invisible Message That Could Save Lives

Updated: Oct 28, 2023


Shutterstock / ambrozinio

You’re driving down a residential street behind a car, when suddenly you see a basketball roll out into the street in front of the car in front of you. Your foot is automatically moving onto the brake pedal, but the car in front of you doesn’t slow down as indicated by the absence of brake lights. Then your fear comes to fruition. A little boy, between seven and nine years old, is chasing the ball out into the street without looking for cars.


You hear the sickening impact of a human body, and the boy flipping into the air like a rag doll thrown upward, and then he comes down hard onto the asphalt street. To your horror, the car that just hit him speeds up. It’s a felony hit and run.

You don’t have time to fumble for your cell phone to take a photo of the idiot. If you try, you’ll miss your opportunity to get a look at the license plate before the increasing distance makes it unreadable. You can’t chase him, because there’s a little kid lying in the street who needs your first aid skills. You release the steering wheel with your primary hand, point, and then using the tip of your index finger like a writing pen, you write the license plate on the inside of your front windshield.

You got it! It’s invisible, but you know from your tactical training that it’s been recorded. You put your car into park, get out of the car, and jog over to the little boy to render first aid. Thank God he’s alive.



When the police arrive to the crime scene, you’re a good witness. You describe the incident second by second. After finishing your account, you suggest to the police officer, “When your Crime Scene Investigations person arrives, you’ll want him or her to ‘dust for prints’ the inside of my windshield.


I used my finger to write down the license plate of the vehicle that struck the boy.” Of course, the police officer knows that sweat and sebum (the oil that moistens and lubricates the fingertips) would leave a residue on the windshield if done correctly. The police officer is astonished that you’d know this trick, and relays the message on the radio.

When CSI arrives, the investigator brushes the inside of the windshield using an extra soft fiberglass fingerprint brush, dipping the end of it into a small container of graphite-based black powder, until the entire surface of the inside windshield has been coated. It looks like a scene right out of a detective movie. Once the process is completed the license plate number looks like it was written with a thick black marker as clear as day. The police officer puts the suspect’s plate number out over the radio, and then after pulling up the registration information the dispatcher broadcasts the information over Red Channel so that all the law enforcement agencies on the frequency for miles around can start looking for the hit and run vehicle.

Here’s another example of how this finger-on-glass trick could save your own life or others. Let’s say you’re being held hostage, either by thugs or terrorists, any you’re sitting next to a mirror, window, or you were allowed to use the toilet in the bathroom. When the hostage taker is not looking, you can write your message for the authorities: the number of bad guys and their descriptions or any information you may have overheard, like where they are going to move you next.


When the authorities arrive at your last know location, where you wrote the note on the slick surface, you can be certain that they are going to “dust the crime scene” for any usable finger or palm prints. When they come across the slick surface you wrote your message on, it will “light up like a Christmas tree.”

There you go. You’re now equipped with another reality-based martial arts technique for your “tactical toolbox.” Of course, “martial arts” literally means “war arts,” and the two scenarios I just described to you are indeed two potential “battles” you, or anyone you train, may one day have to face. BE A HARD TARGET


Jim Wagner

That gray beyond the windshield represents any crime you may witness on the road, and the vehicle in front of you is trying to get away. There’s no way you can get to your phone or grab a pen before the license plate gets too far away to read.


Jim Wagner

Using the tip of your index finger, you write the suspect’s license plate on the back of your windshield as if your finger were a big marker.


Jim Wagner

When the police arrive, a Crime Scene Investigator, per your instructions, “dusts for fingerprints” on the back of your windshield.


Jim Wagner

The black magnetic dust clings to the oils excreted by your finger, and the license plate number you wrote shows up clearly, provided you applied enough pressure and spaced the numbers and letters evenly.


Jim Wagner

The suspect’s license number is “123ABC,” and the police officer transmits it to the dispatcher, who in turn puts out a broadcast to all units. You did your part as a good citizen.

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