OSD 293: How big a magnet do you need to stop a SWAT team?

Stop door kickers with this one weird trick.

Three-inch screws and a reinforced door jamb are good ways to prevent your door from being kicked in. But instead of that hassle, have you considered putting an MRI machine in your home?

A Los Angeles radiology clinic sued the LAPD this week after an officer inflicted at least $60,000 in damage on an MRI machine during a botched raid:

The lawsuit alleges that one of the defendants, Officer Kenneth Franco, who was assigned to the narcotics enforcement detail for the LAPD’s North Hollywood Division, provided false probable cause statements to support an Oct. 12, 2023, search warrant application for the raid.

Franco, a 15-year veteran of the LAPD with a dozen hours of narcotics training, allegedly conducted surveillance at NoHo Diagnostic several times in 2023.

However, Franco failed to consider that NoHo’s high electricity usage, which he attributed to cannabis cultivation, was likely caused by the operation of the MRI machine and other medical equipment, or that tinted windows were installed for patient privacy, the suit states.

On Oct. 18, 2023, Franco and other LAPD officers searched NoHo Diagnostic and detained its lone on-site employee.

An LAPD officer dangling a rifle in his right hand with an unsecured strap entered the MRI room, ignoring a magnetic field warning sign on the door that displayed photographs of prohibited metal objects such as scissors, screwdrivers, keys, watches, and credit cards, the suit states.

MRIs use liquid helium to keep the magnets inside cool and create an extremely powerful magnetic field. When the officer walked into the MRI room, the machine ripped his rifle out of his hands, sticking it to the machine with superhuman force. Then what happened?

Rather than seeking assistance from the on-site employee, the officer allegedly made a “unilateral decision” to activate a sealed emergency button on the machine resulting in the evaporation of about 2000 liters of [liquid helium] and extensive damage to the device.

For context, liquid helium costs $30-50 per liter, and MRI machines cost from $200,000 to $1 million+, depending on features and image quality.

After purging the helium and deactivating the magnet, the officer picked up his rifle and beat a hasty exit, presumably while yelling at the machine to stop resisting. In his haste he left a loaded mag on the floor.

The obvious tactical lesson from this is that you can simply replace the Tannerite-stuffed dog in your foyer with a refurbished MRI machine. But how big a magnet will you need?

That’s a surprisingly complicated question. The force exerted by a magnet depends on its size, shape, temperature, and composition. It also depends on the size, weight, position, and composition of the object being attracted. Different forces can be exerted upon different points of the object, and that all changes in real time as the object moves.

A paper in the Journal of Magnetic Resonance Imaging supplies this helpful image:

The black mass in the middle is an MRI with a fairly typical magnet strength (technically magnetic flux density) of 3 tesla. The color gradient outside the black mass is the force with which ferrous metal objects will be pulled towards the machine. That force is expressed in the chart’s legend as a multiple of the object’s weight. Counterintuitively, the heavier an object is, the more forcefully it will pulled towards the machine. So the heavier the iron that the SWAT team brings, the more they’re helping your MRI do its thing.

You can also see that the magnet’s strength drops off quickly with distance. It drops as the inverse cube of the distance, so if you double your distance from it, you’ll experience it as 2^3=8 times weaker. Triple your distance and it’s 27 times weaker. And so on.

In the diagram, at 2-3 meters away from your MRI machine, the SWAT team will experience 5 millitesla of magnetic strength. That’s the same as a typical refrigerator magnet. You’ll need to move the MRI machine closer to the expected point of entry. Get it to within one meter of the door. At that distance, ferrous metals will be attracted to the machine with a force of 10 times their weight. Let’s estimate a typical ferrous metal loadout:

• Rifle: 2 lbs of ferrous metals. 1.5 lbs in barrel and muzzle device, 0.5 lbs in bolt carrier group.

• Pistol: 0.75 lbs in a Glock 17 upper

• Miscellaneous: 1 lbs total estimate for belt buckle, cuffs, baton, or other steel accessories

• Total: 3.75 lbs

So officers passing within 1 meter of your entrance hall MRI machine will experience a sudden 37.5 lbs push in the direction of the machine. That’s not enough to do much, but coming on by surprise, it would cause an unsuspecting person to stumble and take one step to regain their balance. If we estimate one step at 0.5 meters, then the officer has cut their distance to the MRI machine from 1 meter to 0.5 meters. Since magnetic field strength changes at 1/distance^3, that half-meter stutter step increases the magnet’s pull by 8x. The officer will now be pulled off his feet and towards the machine with 300 lbs of force. The force will escalate rapidly as he closes the distance, maxing out at several thousand pounds of force per officer. That’s with our estimated standard loadout of 3.75 lbs of ferrous metals per officer. Multiply everything by 10 for the officer holding the battering ram.

Here are some refurbished 3 tesla MRIs for sale, starting at a cool $139,500. Liquid helium costs and delivery from Moldova not included.

There you go, you’re immune from SWAT raids. Just make sure to use a different entrance when you come home.

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This week’s links

Brandon Herrera launched a gun store

Pretty cool, you can buy straight from distributors to avoid retail markups.

On some recent themes

Once a Hezbollah operative is identified, his daily patterns of movements are fed into a vast database of information, siphoned off from devices that could include his wife’s cell phone, his smart car’s odometer, or his location. These can be identified from sources as disparate as a drone flying overhead, from a hacked CCTV camera feed that he happens to pass by, and even from his voice captured on the microphone of a modern TV’s remote control.

Relevant previous OSD newsletters:

OSD 269: The social credit system has missiles now

OSD 285: Benjamin, get the musket

OSD 292: For whom the pager tolls

Houston police officer convicted of felony murder for a SWAT raid in which a married couple were shot dead after grabbing a gun

The couple never knew it was the police coming into their house. The specifics of the felony murder charge is that the officer lied on the warrant application, falsely claiming to have conducted a drug buy at the couple’s house.

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