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Episode 59: Crimes and MythDemeanors II

  • Fingerprint scanners can't be defeated: busted (broke both a computer scanner and a 'never been defeated' door lock)
  • Ultrasonic motion sensors can't be defeated: busted
    • ... a shag rug costume: busted
    • ... a bed sheet: confirmed
    • ... walking slowly: confirmed
  • Thermal sensors can't be defeated: busted. You can defeat a thermal motion alarm with
    • ... cooling yourself with a fire extinguisher: busted
    • ... wearing a neoprene suit: busted
    • ... covering your body in mud: busted
    • ... increasing the temperature of the room: busted
    • ... a pane of glass: confirmed
  • Bypassing a glass-relocker safe with water and explosives: plausible. Numerous problems with this technique, though.

See Great Hollywood Heists/Crimes and MythDemeanors I

I loved this episode. It had a bit of everything that makes MythBusters great: surprising results (beating a motion sensor with a bed sheet), explosions, and ridiculousness (Kari dressing up in a yellow shag suit, Tory covered in mud, etc...). The first Crime and MythDemeanors episode was great fun as well, but this one had a greater level of success in defeating the sensors.

Fingerprint Scanner Lock

The big target for this myth was a door lock that the manufacturer claimed had no reported instances of ever being defeated. This door lock incorporated several "live-ness" sensors, including sensors for body temperature, pulse rate, and galvanic skin response, which upped the ante. Grant installed the fingerprint door lock and coded to his own fingerprint.

Grant: "I have the master fingerprint"
Adam: "The Master Fingerprint"
Jamie: "Aren't you special?"

Adam and Jamie were a bit stumped at first as to how they were going to defeat the fingerprint door lock, with Jamie's first idea being a hollow rubber thumb with turkey baster inside (to make it pulse).

Covertly obtaining Grant's print

Adam and Jamie's first mission was to covertly obtain Grant's fingerprint. They went the easy route and had Kari trick Grant. Kari had Grant burn a CD and was able to lift a print from it.

Grant: "Yes, I told the producer yesterday that it would be almost impossible to covertly get my fingerprint. Apparently, I was wrong"
Kari: "You weren't expecting a double agent, were you?"
Grant: "Yeah -- from my own team!"

Cheap biometric thumb scanner for computers

They felt that a cheap fingerprint scanner for computers would be an easier target than the door lock, so they could test some of their ideas on it first. They used the APC Biometric Password Manager, which retails for about $50.

Their main challenge was getting a good print. They first tried using forensic dust on a fingerprint that Jamie left on a piece of glass. They result wasn't very photographable, so they then decided to stick the print and superglue in a vacuum chamber. Much like an episode of CSI, the superglue fumes adhered to the fingerprint and they were able to get a much better print when they dusted it.

Now that they had the fingerprint, they had to create a print of it that they could defeat the computer scanner with. They tried three different versions:

  • Paper print of Jamie's fingerprint: They made a photocopy of the print and placed it on the scanner, but the print was too 'muddy'. access denied
  • Ballistics gel print of Jamie's finger: This was a many step process in order to create a ballistics gel print off of a etched copper board. They first printed out Jamie's print onto acetate. Then they created a raised version of the print using a copper-coated circuit board. The circuit board is coated with a photo-reactive material, and by laying the acetate print on top and exposing it to light, they were able to leave a copy of the print on top. Then they immersed the board in acid in order to etch away the copper, leaving a raised print. Finally, they made a cast on top using ballistics gel. access denied. The print still wasn't clear enough for the computer as the edges weren't defined enough.
  • Ballistics gel print II (cleaned up): Jamie had the idea of enlarging the fingerprints, tracing over them in sharpie to clean up the jagged portions of the print, and then creating the ballistics gel print. access granted

Grant's Fingerprint Scanner with "Live-ness" sensors

With the computer scanner finally defeated, they went onto the actual door lock challenge. This had the additional challenges of the live-ness sensors and the knowledge from the manufacturer that it hadn't been defeated before.

  • Latex copy of Grant's print: Adam made a latex copy of Grant's print and stuck it on his own thumb. Adam's first couple of tries failed, but then he decided to lick the latex: door lock defeated. confirmed
  • Ballistics gel thumb: the door lock was easily defeated by Jamie's ballistic gel print. confirmed
  • Photocopy of Grant's print: Adam licked a piece of paper with Grant's print and stuck it on the scanner. confirmed

Three for three, the MythBusters annihilated the door lock. The door lock was easier than the fingerprint scanner, as even the photocopy defeated the lock.

Thermal Motion Sensor

The thermal motion sensor looks for a large, abnormal area of infrared light. The MythBusters tried various techniques to defeat the sensor -- they had an advantage in that they had a thermal camera they could use to judge the techniques before sending Tory into the room to defeat the sensor.

  • CO2 fire extinguisher: Kari blasted Tory with the fire extinguisher and then he went over into the room with the thermal sensor to see if he could get past -- no luck. Although the thermal camera showed his signature being cooled, it wasn't enough to fool the sensor. busted
    • Neoprene suit: Tory put on a neoprene suit and hood to mask his body signature. As he put the suit on, the thermal camera showed him blending in with the background perfectly. Grant: "Dude, you do look like a ninja". However, the longer that Tory stayed in the suit, the hotter it got, and the alarm went off when he entered the room with the thermal sensor. busted
    • Mud (Predator-style): They plastered Tory in mud, which the thermal camera showed was masking his heat signature. Much like the neoprene, though, his own body heat warmed the mud up and the alarm went off. busted Tory: "If I was trying to break into a building covered in mud, I think it would probably be pretty easy for the police to find me because they would just follow my tracks"
    • Increasing the temperature of the room: They raised the temperature of the room to 98 degrees and Grant entered the room "commando-style" (boxers only). As soon as his leg poked through the ceiling, the alarm went off. busted
    • Pane of glass: Glass can filter infrared light, which is used by the thermal sensor. They felt that it would be unrealistic to carry around a human-sized sheet of glass as you are trying to break in, so instead Kari deployed a small piece of glass over the top of the thermal sensor using an arm that Grant made. Kari and Grant were able to drop into the room undetected confirmed.

Summary: you can defeat a thermal motion alarm with * ... cooling yourself with a fire extinguisher: busted * ... wearing a neoprene suit: busted * ... covering your body in mud: busted * ... increasing the temperature of the room: busted * ... a pane of glass: confirmed

Thermal motion alarms are unbeatable: busted

Water Safe

Myth: you can bypass a glass-relocker by filling a safe with water and then detonating a charge inside the safe, as illustrated in the film The Score

A glass-relocker is a pane of unbreakable glass within the safe itself that, if broken, activates locks that makes the safe impenetrable. The idea with the technique demonstrated in The Score is to blow the door off the safe and render the glass relocker moot. The water more efficiently transmits the energy of the explosion to the outside of the safe.


  • Safe with glass-relocker: 6' tall, 8" thick walls, 3000 pounds
  • South San Francisco Water Quality control plant, i.e. sewage treatment plant. They set the safe in one of the empty troughs, i.e. sewage treatment troughs.

They took apart the safe before running the experiment to inspect the glass relocker. Adam thought the glass-relocker would cover the entire face of the vault. As it turns out, the glass-relocker was a small pane of glass just covering the tumblers.

Their regular explosives expert, Frank Doyle, was on-hand to set the charges.

The 5-step process

  1. Bore a hole in the top of the safe with a thermal lance
  2. Fill safe with water
  3. Lower explosives into save
  4. Blow door off the safe
  5. Get the money and run

The Run

Step 1: Bore a hole in the top of the safe with a thermal lance. It took Adam 10 minutes to break into the safe using the thermal lance, using a dozen or more iron rods for the lance. This was much longer than it took in the movie, and much worse, the lance incinerated the contents of the safe.

Step 2: Filling the safe with water. When they first started filling the safe with water, the water immediately started leaking out of the safe. Adam and Jamie sealed the outside of the safe using butyl tape, which Jamie has used to seal a boats underwater. Even with the butyl tape, the leaks still got worse as more water went in. So they had to resort to opening the safe and sealing it with foam... something a robber can't exactly do.

Step 3: Lower explosives into safe and Step 4: Blow door off the safe. The safe and door went flying in different directions, and the door landed 30 yards from the safe. The walls of the safe had also blown out a bit. Jamie: "I think we're inside the safe." By this point, the loot was pretty-well damaged.

Jamie: "They may well have relocked the door, but if the door isn't in the safe anymore, it doesn't do them very much good"

There were numerous problems with this myth: lengthy time to bore a hole into the safe with a lance, incinerating the contents of the safe, sealing the safe so you can fill it with water, soaking your prize in water, and damaging the contents in the actual explosion. However, as they heard the movie was based on an actual robbery from the 50s, which they were able to find no corroborating evidence of, they still deemed this one plausible.

Ultrasonic Motion Sensor

An ultrasonic motion sensor sends out a high-frequency sound wave that bounces around and creates a pattern. If anything disrupts that pattern, the sensor is set off.

  • Shag rug costume: Kari made a Big-Birdish costume out of a yellow shag rug she bought at Therapy Furniture in SF. Her hope was that the thick carpeting would absorb the ultrasonic signal, but it failed to defeat the sensor. busted
  • Bed Sheet: Kari held up a bed sheet in front of her as she walked through the corridor -- the alarm didn't go off. confirmed. Kari: "This is stupid. You know when you get that list of myths and you're like, come on, This was on the list of 'alright lets just get this over with and fail it' so we can get onto something might actually work"
  • Walking slowly: Kari took 20 minutes to slowly traverse the short hallway, but she made it through without setting off the alarm. confirmed

Ultrasonic motion sensors can't be defeated: busted


I'd say the idea of defeating infrared sensors with mud wasn't "busted". What they showed is that it worked temporarily. With regard to the "Predator" film, I would say they showed the first scene based on the idea (where Ahnold accidentally falls in the mud) "plausible", but busted the finale.