CFL Key & Lock Examination 3 — Questions and Answers
Question 1: Which evidence of forced entry in a pin tumbler lock is MOST associated with bumping attacks?
- Bent or deformed plug face
- Radial scratches around the keyway from a pick
- Uniformly distributed impact marks on all pin chambers (Correct answer)
- Shear line scoring consistent with a single tool
Correct answer: Uniformly distributed impact marks on all pin chambers
Bump keys cause the driver pins to momentarily jump simultaneously, leaving characteristic impact marks across all pin chambers rather than sequential picking marks.
Question 2: A forensic locksmith examines a padlock shackle and finds transverse (horizontal) saw marks. This evidence MOST suggests:
- Drilling of the lock cylinder
- Cutting of the shackle with a saw or bolt cutters (Correct answer)
- Picking with a diamond pick
- Shimming of the shackle locking mechanism
Correct answer: Cutting of the shackle with a saw or bolt cutters
Transverse saw marks on a shackle indicate it was cut with a hacksaw or similar tool, a common forced entry method targeting the exposed shackle.
Question 3: What forensic significance do 'witness marks' have in lock examination?
- They indicate the lock's last legal use date
- They show contact points between moving parts, revealing manipulation history (Correct answer)
- They are manufacturer inspection stamps required by ALOA
- They measure the plug's rotational tolerance
Correct answer: They show contact points between moving parts, revealing manipulation history
Witness marks are transfer impressions left where two parts have contacted each other, revealing how and whether components were manipulated.
Question 4: When a lock plug shows extensive circumferential scratching around its outer diameter, a CFL would MOST likely conclude:
- The lock was exposed to harsh weather conditions
- A plug follower was improperly used during rekeying
- The plug was rotated against the shell without a key, suggesting picking or bypass (Correct answer)
- The lock was manufactured with improper tolerances
Correct answer: The plug was rotated against the shell without a key, suggesting picking or bypass
Circumferential scratches around the plug's outer diameter indicate the plug rotated without a proper key, which occurs during picking, decoding, or bypass attempts.
Question 5: In a forensic examination, 'false set' in a lock refers to:
- A lock that opens with multiple keys
- A secondary rotation point that occurs during picking when spools or serrated pins are present (Correct answer)
- The incorrect installation of a deadbolt throw
- A counterfeit lock that mimics a higher-security product
Correct answer: A secondary rotation point that occurs during picking when spools or serrated pins are present
A false set is the slight plug rotation felt by a picker when serrated or spool pins partially set, which is a key indicator that anti-pick pins are present in the lock.
Question 6: What does examining the bottom of the keyway (warding) tell a forensic locksmith?
- The number of pins in the cylinder
- Whether the lock has been re-keyed
- Whether the suspect key is compatible with the lock's keyway restrictions (Correct answer)
- The manufacturer's recommended lubricant type
Correct answer: Whether the suspect key is compatible with the lock's keyway restrictions
The warding profile determines which key blanks can physically enter the lock, so examining it helps determine if a suspect key could have operated or entered the lock.
Question 7: A forensic examiner finds that the springs in a lock cylinder are all deformed in the same direction. This finding MOST suggests:
- Normal spring fatigue from long-term use
- Overpressure from excessive tension wrench force during picking (Correct answer)
- Manufacturer defect in spring tempering
- Drilling damage to the spring chambers
Correct answer: Overpressure from excessive tension wrench force during picking
Springs deformed uniformly in the same direction often result from a tension wrench applying consistent rotational force while picks manipulate the pins, compressing springs abnormally.
CFL Key & Lock Examination 3
Which evidence of forced entry in a pin tumbler lock is MOST associated with bumping attacks?