The Stapled Bag and the Reassembled Padlock
At 02:40 a storage-facility manager reports a unit door standing open. The unit is secured by a laminated steel padlock with a hardened shackle. The responding officer cuts the shackle with bolt cutters so he can enter and check for a suspect. He places the two shackle pieces, the lock body, and a key he later found in a suspect's jacket into a single 20 x 30 cm plastic zip bag, writes the case number on the outside with a marker, and staples the bag shut. Four hours later, at the property room, a detective removes the lock, fits the two shackle pieces together, inserts the key, and turns the cylinder to confirm it works; he then returns everything to the same bag. The key is entered into evidence three days later, after the detective finishes his report. No photographs were taken of the lock on the hasp, and the hasp itself was not collected. At trial, defense counsel asks the locksmith whether the key operated the lock at the time of the offence.
1. Identify each chain-of-custody and preservation failure and explain how each can affect the evidence.
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Failures and effects
- All items in one container. Lock body, cut shackle, and key contact each other. Trace and DNA transfer between the key and the lock becomes meaningless, and the key's association with the lock is weakened.
- Staples instead of a tamper-evident seal. Staples can be opened and re-closed invisibly. There is no initialled, dated seal and no record of who opened the bag.
- Function test before documentation. The detective turned the cylinder before the lock was examined or photographed in its received condition. Cylinder position, keyway condition, and any marking inside the plug are now altered.
- No in-place photographs and no hasp. The lock's relationship to the door, the hasp, and the cut is unrecorded; the hasp could have carried tool marks matching the bolt cutters or other tools.
- Three-day delay in entering the key. The key's whereabouts and handling for three days are undocumented, and the officer-to-detective transfer is unlogged.
Legal effect
These go to weight, not automatic exclusion. The defence will use them to argue tampering or substitution. The examiner must not paper over the gaps; the report should state the history known and the limits it imposes.
2. What examinations remain defensible, and what must you now avoid saying?
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Still defensible
- Decode the key's bitting and measure the cylinder's pinning; compare them. If they correspond, the key is cut to the lock's combination.
- Examine the cut shackle faces for tool marks and compare with the bolt cutters if they were retained. The two halves can often be matched to each other and to a cutting tool.
- Document the lock's construction, any manufacturer markings, and whether the cylinder shows picking or bumping damage.
- Compare the key to the lock's keyway profile as class evidence.
Now compromised or unavailable
- Any claim about the cylinder's position at seizure.
- Any claim that the key was the one used at the offence. The post-seizure function test proves only that the key operates the lock in its current, cut, reassembled condition.
- Trace or DNA linkage between key and lock, given co-packaging and handling.
- The hasp and its tool marks are gone.
Prohibited phrasing
Do not write the key operates the lock, confirming the suspect opened it. Do not describe the function test as an examination of the offence condition without disclosing that the shackle was cut and the lock handled first. Disclose every gap in the report body, not only under cross-examination.
3. Draft your answer to defense counsel's question: 'Does this key operate this lock?'
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Model answer
Yes, in its present condition. I decoded the key and compared it with the cylinder's pinning, and the cut depths correspond to the lock's combination within measurement tolerance. I also tested it and the plug rotated. However, you should understand what that test does and does not show. The lock was cut off the hasp with bolt cutters before seizure, all components including the key were carried in one unsealed, stapled bag, and a detective fitted the shackle pieces together and turned the key four hours after seizure, before I saw it. My test therefore confirms that this key is cut to this lock's combination and operates it now. It cannot establish that this key was used at 02:40, that it was the only key, or that the cylinder was in this position when the officer arrived. The original hasp was not collected and the lock was not photographed in place.
Then stop. Do not speculate about what the suspect did. If asked whether the handling could have changed the result, answer directly: the bitting is physical and unaffected by handling; the handling affects association and the interpretation of the earlier test, not the cut depths.