Knife detectors are apparently a thing now (but are unreliable).

[glistam]

I'm posting this under "Knife Laws" because it's related to a way knife restrictions can be enforced.

A short while ago I went on a trip to DC to visit the museums, many of which are owned and run by the federal government. I hadn't been back in several years and so I was operating under the assumption they still had their previous security procedures: The body is off-limits, but they check any bags. This apparently is no longer true.

When you arrive at these museums, they have a security guard wave people one at a time in between these two metal columns. When it detects "something" a red light turns on and there is an relative unobtrusive beep. Neither the device nor the guards seem all that bothered when it goes off, but anyone it does sound off for is sent to a second line where a guard has you set your bag on the table and asks you to open the pockets (they don't seem keen on touching the bag, except with a stick).

It went off for me and so I took my bag over to the side. After showing the contents, that guard had me walk through again without the bag, and it beeped again. The first thing he said was "Do you have like, a glasses case, or some other thin metal thing that might that might terminate in an edge?" I was confused how this thing was supposed to work so I started listing metal things I was carrying, occasionally pulling them out of a pocket to show. Hilariously, I had OC spray and a Surefire light on me, and they were like "Nope, that's fine. What else?" Eventually I got my key-ring out and they saw a little 1.5" slipjoint on that. The guard says "Yeah, there's the problem." I asked him why, since the law for federal locations normally allows 2.5" or less. I showed my federal ID and told him about my work facility. He said that was true, but they don't allow any knives because of the artwork. I assume he's alluding to incidents like in Denver a few years ago were a mental deranged person slashed up a $3 million painting with a razor. When I explained how it doesn't actually say that anywhere on the front door or the website, he admitted they could do better with warning people, but it wasn't his call. He was very chill about the whole thing, and offered to hold my knife in his pocket and let me through. He gave it back when I was leaving. I returned the next day having completely removed everything from my pockets ahead of time, and only carrying a camera bag. Same guard was there. The detector still went off, but this time he was satisfied by just looking at the stuff in the camera bag, and let me through.

I'm not sure how this stupid thing is supposed to work, but it's clearly not reliable. The day two visit shows that the flat metal internals of my camera, like the aperture, are enough to set it off, as are things like cases for glasses. The enforcement is also very poor, as they found my slipjoint, but didn't press any further and thus missed the three other knives I was carrying . I don't mind admitting that because, as the guard stated, the knives don't violate any laws, just that particular location's policy. Good thing I wasn't a nutcase.

Anyway, just wanted to warn people that tech like this is out there now, even if it's still kinda garbage.

 

[SomebodySomewhere]

Deleted.

 

[tinfoil hat timmy]

yup. super dumb

 

[tom19176]

It sounds like a pretty standard metal detector system unless I am missing something. They can be adjusted for sensitivity.

 

[madcap_magician]

My workplace has similar scanners in place at major patient entrances now. They are 'passive weapons detectors' made by Evolv, but I suspect it's basically a not-very-bright AI algorithm and a metal detector. I laugh in Work From Home next to my desk covered in guns and knives.

 

[glistam]

It sounds like a pretty standard metal detector system unless I am missing something. They can be adjusted for sensitivity.

Metal detectors simply can tell if certain substances pass by, but according to an article I read, these can sense the approximate shape of the object if it's a ferrous material. Like cylinders for gun barrels, and flat shapes for knives It's just that shape alone isn't a reliable indicator of the object being a weapon.

 

[hhmoore]

My workplace has similar scanners in place at major patient entrances now

I've been awaiting them at mine as they've had the signs up for years.

 

[madcap_magician]

Metal detectors simply can tell if certain substances pass by, but according to an article I read, these can sense the approximate shape of the object if it's a ferrous material. Like cylinders for gun barrels, and flat shapes for knives It's just that shape alone isn't a reliable indicator of the object being a weapon.

If it's Evolv, the company is super cagey about this for intellectual property reasons, but they've become really big in the Security Theater Industry, and their scanners are in use at a lot of big places like concert venues, stadiums, schools, and other high-throughput places where scanning has to be fast and run a lot of people through in a short amount of time. But, some investigative journalism I've seen suggests that it's still got the same problems and general error rate of normal metal detection systems, and that if you set it for high sensitivity, it gives a lot of false positives and slows the processing queues, and if you set for low sensitivity, it misses a lot of actual weapons.

That is the general idea though, it can detect shapes that are likely to be weapons. It's a dark comedy at my workplace, of course, since there are hundreds of public entrances alone, not to mention employee entrances, and only four or five have screening, and the 'security ambassadors' who man them just tell you to return whatever you had to your vehicle; so, you know, the only people they're stopping are people with pocket knives and concealed-carry permits who had no ill intent. Plus people with laptops and large tablets who get really annoyed at getting stopped.

But if I have to go on campus, I just go through a different entrance, because who has time for that nonsense.

 

[King of the Cheese]

It’s not a metal detector. It’s an AI scanner that I assume runs data through a system to scan for people that are likely to have a weapon or firearm on them. They probably mix in some random screening so people can’t figure out how to “beat it”. If I had to guess, it’s looking at facial expressions, clothing profiles (shapes in your waist and pockets). I went through okay but two 50-something year old women had their purses searched. Had a SAK on me at the time and forgot. My guess is it is that it’s use is limited, but it keeps people guessing.. so people that might be trying to beat metal detectors are kept on their toes (or discouraged) from entering.

 

[madcap_magician]

It’s not a metal detector. It’s an AI scanner that I assume runs data through a system to scan for people that are likely to have a weapon or firearm on them. They probably mix in some random screening so people can’t figure out how to “beat it”. If I had to guess, it’s looking at facial expressions, clothing profiles (shapes in your waist and pockets). I went through okay but two 50-something year old women had their purses searched. Had a SAK on me at the time and forgot. My guess is it is that it’s use is limited, but it keeps people guessing.. so people that might be trying to beat metal detectors are kept on their toes (or discouraged) from entering.

That's mostly incorrect. The data input is from active sensing systems like millimeter-wave or backscatter x-ray, and that in turn is analyzed by AI algorithms. It's not limited to detecting metal, it detects things of varying densities and size, and the algorithms flag suspect items based on the system operator's criteria. Some of them are... not very bright. Evolv had problems for a long time thinking that umbrellas were rifles. I think you're definitely right about the 'keep people guessing' part. All crowd scanning systems have operator-set sensitivity levels, and you can't guarantee catching everything and get any number of people through with any speed, so more than half the benefit is probably from having visible screening checkpoints, deterring people maliciously trying to smuggle things past, and remind normal people to check themselves.

 

[King of the Cheese]

That's mostly incorrect. The data input is from active sensing systems like millimeter-wave or backscatter x-ray, and that in turn is analyzed by AI algorithms. It's not limited to detecting metal, it detects things of varying densities and size, and the algorithms flag suspect items based on the system operator's criteria. Some of them are... not very bright. Evolv had problems for a long time thinking that umbrellas were rifles. I think you're definitely right about the 'keep people guessing' part. All crowd scanning systems have operator-set sensitivity levels, and you can't guarantee catching everything and get any number of people through with any speed, so more than half the benefit is probably from having visible screening checkpoints, deterring people maliciously trying to smuggle things past, and remind normal people to check themselves.

It’s not “incorrect”, you’re “incorrect” in mentioning anything about “metal detection”. It absolutely is not a “metal detector”, as I’ve already explained I’ve gone through with knives unchecked and I know people with pacemakers that can walk through them. In short, they’re like advanced forms of the machine at the airport checkpoint you put your arms up inside of, but they also have an AI element for predictability that they don’t discuss.

Edited to add: These machines are less about the individual and more about preventing mass casualty events at large public gatherings or larger places of employment. They aren’t made to bust the guy with a pocket knife. More so people carrying explosives and firearms.

 

[jstrange]

Metal detectors simply can tell if certain substances pass by, but according to an article I read, these can sense the approximate shape of the object if it's a ferrous material. Like cylinders for gun barrels, and flat shapes for knives It's just that shape alone isn't a reliable indicator of the object being a weapon.

Yep, Disney has something like these at their parks now. I can definitively state they are bad at detecting miniature liquor bottles.

 

[madcap_magician]

It’s not “incorrect”, you’re “incorrect” in mentioning anything about “metal detection”. It absolutely is not a “metal detector”, as I’ve already explained I’ve gone through with knives unchecked and I know people with pacemakers that can walk through them. In short, they’re like advanced forms of the machine at the airport checkpoint you put your arms up inside of, but they also have an AI element for predictability that they don’t discuss.

Edited to add: These machines are less about the individual and more about preventing mass casualty events at large public gatherings or larger places of employment. They aren’t made to bust the guy with a pocket knife. More so people carrying explosives and firearms.

I didn't say it was a metal detector. I said it is capable of detecting metal, among other things, and that the algorithms identify potential weapons by their size, shape, and density. The fact that you've gotten through with knives unchecked and that people with pacemakers can walk through them is irrelevant, because as I said and you did not read, security scanning systems like this have variable sensitivity settings that the user can configure where the system will only alert for items of a certain size, shape or density threshold.

Hence, as I said, the operator decides what sensitivity level they want to use for their facility by balancing inconvenience and higher rates of false positives against their policies and the sensitivity of their security needs. Even at airports security scanners are set with a sensitivity threshold to not generally alarm for small medical devices with minimal amounts of high-density components, or operators are trained to identify and ignore such devices, and in places like shopping malls where there may not even be a policy against firearms per se, they'd be set with a much more liberal sensitivity threshold so as not to be triggering alarms over every single metal pen, large smartphone, pocket knife, or umbrella, since the operator does not care about those things.

Were you to try doing the same thing in a higher-security facility using stricter sensitivity settings on their scanning equipment, the odds of you getting through with a pen knife would go down drastically. The purpose of these machines is whatever the operator wants it to be. For the most part, you're right, it's about people with firearms or explosives. But, if the operator wanted to run a high-security installation and bust everyone with a pocket knife, they could start a line and run their scanner settings to detect knives, and they'd probably be mostly successful.

Now, I am not an owner or operator of this type of security equipment, all I know is from some brief online reading that I did when my employer installed these devices, so other than what I've said I'll defer to your expertise in their operation and function derived from having walked through a scanner a few times.

 

[King of the Cheese]

I didn't say it was a metal detector. I said it is capable of detecting metal, among other things, and that the algorithms identify potential weapons by their size, shape, and density. The fact that you've gotten through with knives unchecked and that people with pacemakers can walk through them is irrelevant, because as I said and you did not read, security scanning systems like this have variable sensitivity settings that the user can configure where the system will only alert for items of a certain size, shape or density threshold.

Hence, as I said, the operator decides what sensitivity level they want to use for their facility by balancing inconvenience and higher rates of false positives against their policies and the sensitivity of their security needs. Even at airports security scanners are set with a sensitivity threshold to not generally alarm for small medical devices with minimal amounts of high-density components, or operators are trained to identify and ignore such devices, and in places like shopping malls where there may not even be a policy against firearms per se, they'd be set with a much more liberal sensitivity threshold so as not to be triggering alarms over every single metal pen, large smartphone, pocket knife, or umbrella, since the operator does not care about those things.

Were you to try doing the same thing in a higher-security facility using stricter sensitivity settings on their scanning equipment, the odds of you getting through with a pen knife would go down drastically. The purpose of these machines is whatever the operator wants it to be. For the most part, you're right, it's about people with firearms or explosives. But, if the operator wanted to run a high-security installation and bust everyone with a pocket knife, they could start a line and run their scanner settings to detect knives, and they'd probably be mostly successful.

In a high-security facility, they’d have metal detectors and wands and make people empty their pockets and bags. They wouldn’t use hit or miss equipment like this.

 

[mobilerd]

Good info. AI is upon us. I’m 66 so hopefully I won’t see a SKYNET situation in my lifetime.

 

[Vlade]

Now they're doing scanning or whatever you want to call it with a wand at the grocery store. Since they changed the gun law many people are carrying concealed. There is a sign that says no guns and no knives. I got popped with my cold steel knife. So I had to just put it back in my car. The scanning seems to become a norm lately.

 

[DMG]

I went to 4 Smithsonian museums last month with a BM Bailout and a AA flashlight in my pocket, as well as a cell phone. I went right through the machines with no problem.

I think they are measuring the amount of metal on you or something similar because metal did not set them off.

 

[bemymonkey]

Whether it's a knife detector or a metal detector or our new AI overlord, these things aren't exactly new. The fact that they're iterating and improving the technology behind them is pretty cool to me as a tech nerd. But the really critical thing is how they're implemented and which policies are followed when something is found.

It's perfectly fine with me if a location wants to restrict people bringing certain things on their premises. It's the same here in Germany: The owner of the property gets to decide what's allowed. The issue is the way things are handled when a pen knife is found. Being denied entry or asked to place your stuff in a locker or back in your car is perfectly fine with me, but most of the cases you hear about here in Germany don't go that way.

We've had cases where perfectly legal (as in the law specifically states you are OK to carry a non-locking folding knife or a fixed blade up to 12cm blade length in public) knives have been detected and escalated to insane levels. People are so unused to knives of any kind these days that even the ones that are explicitly legal cause fear and suspicion. Add that to the fact that the people running these security checkpoints are usually stressed and nowhere near sufficiently trained, stupid things happen. I'm talking about things like a Spyderco UKPK causing the cops to be called and the very uninformed cops confiscating the knife and starting a civil case against the owner... IIRC that one actually ended up with a substantial fine.

A few weeks back they were talking about a kid getting caught with one of those credit card knives in his backpack. Perfectly legal to carry, really hard to hurt someone with, and still the cops were called.



Eh... Maybe idiots just need to stop stabbing people...

 

[Enkrig]

As someone that lived in Europe, I used to think that it was ok to restrict certain "dangerous" knives. Still, at that time, I could use a knife in front of the cops and, as I long as I wasn't being a jerk, they wouldn't even bat an eye. I think that the many countries in the world have become so unreasonable and outrageous that I think that we all ought to stand together and say that enough is enough! If one is not breaking the law, that is unlawful detention. I will always accept someone saying "I don't know and need to double check", but ignorance with arrogance is never acceptable.

In the US, I would first have them drop the changes (it is a lawful knife after all) and then sue them for unlawful seizure of private property, legal fees, and compensation for unlawful detention. In the same way that all of us need to educated in the law and ignorance is not an excuse, the same has to be held regarding the police. If anything, they ought to be held to a higher standard because they are professionals and their actions can severely damage people's lives.

There will always be criminals during bad things. And the police should chase those criminals. But why should our liberty be restricted if we have done nothing wrong? A core tenet of western justice systems is "innocent until proven guilty", but these restrictions treats us as if we were all criminals-in-the-making. Very disconcerting.

 

[DocJD]

I now always wear my special aluminum foil bodysuit and lead lined underwear , if I expect to be scanned by AI perv peeping-toms !