This Man Will Take Your Picture While Macing You


Odds are you don’t have a photographic memory, so if you ever have to mace someone, you probably won’t remember exactly what your attacker looks like. Compound that with talking to the police and looking at a few dozen mug shots, and it’s highly unlikely you’ll ever be able to identify the person you maced. This was the problem [John], [Cordelia], and [Adrian] chose to solve for [Bruce Land]’s microcontroller course at Cornell this semester.

The device they created, PepGuard, adds a microcontroller and a serial JPEG camera to a canister of pepper spray. When the button on top is pressed, the microcontroller flashes a LED, takes a picture with a camera, and sends that picture to a phone over a Bluetooth connection.

PepGuard is always connected to the user’s phone via Bluetooth, and this allows for some interesting possibilities. With their Android app, the team can set up the phone to call emergency services when the device is activated.

You can check out the demo of the device after the break, or read the team’s report here.



40 thoughts on “This Man Will Take Your Picture While Macing You

  1. It is a good idea until the perpetrator finds out you took a picture of him. When he does I hope you’re Usain Bolt or Wonderwoman because that person will do anything in their power to get that image away from you.

    Besides that, really really good idea.

    1. That is a point worth considering. I’m not sure how much it matters in practice though: “and then I maced the f###er” is probably part of the victim’s police report anyway, and I doubt many victims today (pre-macecam) would spray the attacker in self-defense and then actively deny doing so.

      1. Unless you have a witness or the person you maced has a history of mugging/rape related crimes or is picked up with weapons/contraband/someone else’s stuff, it’s a he said/she said.

        1. The macing is *not* a “he said/she said” situation. The victim of the (alleged) mugging/rape/etc is saying the same thing as the perpetrator with regard to the macing. So proof that you maced somebody is of no relevance when you’re already claiming to have maced somebody.

          The situation leading up to the macing certainly can be a “he said/she said” situation, but the macing itself is not.

          In other words, when I’m being mugged and I mace the mugger, I tell the police “I was being mugged and I maced him.” He might say “I was minding my own business and that jackass maced me.” So the events leading up to the macing are in question, but we *both* say that I maced him, so proof of that event doesn’t much matter since I’ve already stated I did it.

    2. Then only help here would be a recording started before the mace/pepper spray is used. Most of the personal protection sprays have a flip up safety lid, protecting the spray button from accidental use. Combine the video recording with the safety flip up, and you have a recording of what happens before the spray is used. Audio too, and even better.

      Recording devices are already included in many devices. AEDs have audio recorders built in, some tasers have video in them already.

        1. At least in the US, I don’t believe this is an issue. It’s my understanding you can legally record anything you would have personally seen or heard. Only when the person has a reasonable expectation of privacy, and they think they cannot be seen or heard by you, is there a problem. Obviously, this doesn’t apply if they’re assaulting you.

          So you could actually do one step better. Record continuously, automatically discarding audio/video older than a few minutes. Upon triggering, permanently retain the recent recordings, along with whatever else that happens within the next few minutes. A secondary trigger to retain recordings *without* macing someone would come in handy too, you never know when you might need it.

          1. It really depends on the state. Recording audio, even in public, has been construed as wire tapping in the past. There have been a few instances of people with video cameras in their cars recording police stops that were charged with wire tapping.
            A man in Maryland was charged and eventually won in appeals, but not everyone has thousands of dollars to burn in legal fees.
            In short check with your state first.

  2. I like the idea. It addresses a very real world issue. Lots of potential here. I think some enhancements could really make it a stellar device:
    1 – I realize this is pretty much assumed as this is a prototype, but a solid form factor. Getting this in a practical size and well integrated with the mace will be one of the biggest challenges.
    2 – On-board storage in case the BT fails. The pictures could be retrieved later via USB. The USB would also provide a convenient charging method.

    I had bought some mace for my wife back when we were dating, and if a product like this was on the market, I would probably get it for her.

    1. I agree. This product has TON of potential and I am sort of surprised it isn’t out there yet. I think the on board storage is critical, and it should be hard soldered, non-volatile, and environmentally hardened, so even if the person manages to grab it and smash it, or throw it in the river, the image will be recoverable. It should also probably keep flashing pictures as long as it is spraying just in case one does not come out.

      I don’t think the battery is a deal breaker either, as long as it lasts longer than 2 or 3 days. You might even be able to incorporate energy harvesting tech to keep it topped off. Add a built in inductive charger, and just place a charging mat where you usually place your purse…

  3. potential brilliant. if such a device with “instant post it somewhere” function get in the hands of the masses it might be a deterrant on it self. you can wash of the mace in your hideout, but removing a picture from the net is almost impossible.

  4. Reading this it all seems so “obvious” yet nobody had done it. I am Rating this Brilliant. Taking things that are already there – phone, bluetooth, mace – and combining them to be more and better than before!

  5. Neat prototype! Of course the final version would need to fit in my purse.

    One thing to consider would be adding a flash, since a lot of macing happens in the dark.

    Also, the bluetooth is a novel integration, but there’s too much fiddleyness for a device like this. Instead i would suggest some onboard spi and a micro b usb connector that you could later use to email Five-O a picture of your assailant.

    Optimally, i guess this thing would run on a coincell battery and would connect to the top of the pepperspray tube via a rubber sleeve.

    As a mugging victim myself, who later had trouble identifying the attacker I would really like to see this developed!

  6. A better method would be to have it lop off their head, then identification is a breeze.

    Seriously, cool idea, but local storage, smaller form factor (perhaps wrapping around a can of mace?) and checking with local authorities to see how much trouble you can get into with this device (the aforementioned “victim” statement) would be good next steps.

  7. I would rather have it store the image in the unit. that way I can give the device to the cops and they can complete chain of custody on the image and make it admissible in court.

    Sending it to the phone is actually a bad idea.

    1. I think doing both would be an even better idea.
      That way best case, go with your plan, as well as not worry about bluetooth being bluetooth.
      But worse case, if the perpetrator snatches the device from you, you’ll have a copy on the phone and not be empty handed.

  8. Make sure you hold your hands still while you defend yourself. That way, you get a better picture of the mugger.

    What do you think the picture will show? The picture will show you macing someone and not someone mugging you. You will be providing the attacker evidence to sue you. A con will get a good lawyer and say his client is the victim and you will go to jail.

    Another thing is that mace carries the same charge as if you used a gun on someone in some jurisdictions.

  9. “PepGuard is always connected to the user’s phone via Bluetooth…”

    That’s a very bold statement. Since when is bluetooth always connected to anything? Bluetooth is a pain in the ass, drops connection, loses pairing, etc… all the time. I’ve never seen even a bluetooth headset that “always” stayed connected. Every blueooth device I have owned, I have to screw with for 5 minutes everytime I want to use it even if it was the last device used. There is no way I would trust that this would actually be connected at the time I need it most.

    If he solved that issue alone, I think that solution would be more valuable than the device itself.

  10. This was cool, but sadly they were 3 years behind. In 2009, at the University of Nevada, Reno we did the exact same project….I wouldn’t be surprised if they found it online and copied it. I do think this should be an open source project though. If someone has some time to sketch up the details and a tutorial that would be awesome.

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