The TV show Mythbusters does it again. On Episode 59: Crimes and Myth-Demeanors 2- Round 2 they attempt to defeat a PIR motion detector, an ultrasonic motion detector and a fingerprint reader / door lock. You can see how difficult it was to finally defeat the Infrared (PIR) by placing a glass frame over it which blocks the temperature sensing.
The ultrasonic was easy- but in reality almost no one uses ultrasonic anymore for that very reason and the fact they are so prone to false alarms.
Also it wasn’t much of a surprise they defeated the fingerprint reader (after 3 days). What they didn’t explain was that most fingerprint / biometric readers require or use a PIN. The PIN is used to “narrow down” the fingerprint choices the processor has to compare when you place your fingerprint on it. Also- all fingerprint biometric readers have a programmable threshold of accuracy. You can set it to require 99% accuracy or anything lower. Since we don’t know how the Mythbusters unit was set, we can’t be certain how easy it was to defeat it.
A final word, commercial fingerprint readers are not state of the art due to the low cost required by the marketplace. They “read” the fingerprint by either an infrared optical scan (of fairly low resolution) and compare it to a stored template; -or- by a galvanic (resistance) reading of your finger.
In the case of the Mythbusters unit it appeared to the optical type. Again the defeat may not have occurred had they had to guess a PIN and/or the accuracy was set to maximum.