Forensic Examination and Documentation of Lock Evidence
Domain 3 tests the examination sequence and the documentation that makes a lock finding defensible later: photographs, measurements, notes, sketches, and a record of every handling step.
Sequence
- Document in place before moving the item: wide shot, mid shot, macro of keyway, bolt, strike, and any tool marks; include a scale and note orientation and handedness.
- Record condition, make and model, serial or stampings, finish, debris, lubrication, corrosion, and pre-existing damage.
- Examine non-destructively first: visual, magnification, oblique lighting, borescope, measurements. Function-test only after documentation, and record the test method and result.
- Label components separately if disassembly is necessary; keep pins, springs, and screws with their cylinder. Photograph the arrangement before removal.
- Maintain contemporaneous notes: date, time, examiner, location, actions, instruments, and witnesses.
Worked example
A rim cylinder is received loose in a bag. Before testing, you photograph the bag seal, label, cylinder face, keyway, and tailpiece. You note the plug is rotated 15 degrees off vertical and the tailpiece is bent. A function test with a known key fails. Because the pre-test condition was recorded, you can later say the bind and bend were present on receipt, not caused by your test.
Traps
- Testing or spraying lubricant before photographs.
- Failing to record lock handedness, mounting orientation, or which side faces the door.
- Mixing pins or springs between cylinders.
- Writing 'lock was picked' when you only observed a mark or a malfunction.
- Omitting the examination date and the identity of everyone who handled the item.