The Deadbolt That Was Extended When the Door Stood Open
At 08:15 a patrol unit responds to a reported burglary at a 1990s tract home. The rear exterior door is found ajar about 10 cm. It carries a Grade 2 single-cylinder tubular deadbolt with a 25 mm (1-inch) throw and a separate spring latch. The deadbolt is fully extended and undamaged, with no marks on the cylinder face or plug. The deadbolt strike plate is bent outward; both 19 mm (3/4-inch) screws are pulled from the jamb and their holes are elongated. A 12 mm deep gouge runs vertically on the jamb face at bolt height, and paint is cracked in a pattern radiating from the strike. The interior thumbturn is in the locked position. The homeowner reports jewelry missing and says she locked the deadbolt at 23:00. No footprints are visible on the concrete stoop, and the yard gate is closed but unlocked. The responding officer asks whether this is a forced entry or a staged scene, and whether the lock should be removed now or left for the detective.
1. The deadbolt is fully extended yet the door stands ajar. List the competing explanations and identify the physical evidence that would separate them.
Read the worked answer
Hypotheses to test
- Frame spread / pry attack. The door was closed and bolted, the jamb was levered away from the door, the 25 mm bolt slipped past the strike lip, and the door sprang open, leaving the bolt extended. This predicts outward-bent strike, screw holes elongated in the direction of pull, a lever gouge at bolt height, and fresh paint fracture radiating from the strike.
- Bolt thrown while the door was open. Someone inside threw the thumbturn with the door ajar. A thrown bolt physically prevents the door from closing, so this predicts no strike deformation and no screw pull-out. The present strike damage argues against it as the sole explanation.
- Cylinder defeat, then staging. Picking or bumping retracts the bolt, entry occurs, and the bolt is re-thrown from inside to simulate a locked door. This predicts no cylinder damage but also does not explain a bent strike or pulled screws; the strike damage would then have to be old or manufactured.
- Latch-only entry with the deadbolt never thrown. The homeowner is mistaken about 23:00. This predicts an undisturbed deadbolt strike and an undamaged bolt, which is not what is present.
Discriminators
Measure screw-hole elongation direction, deformation direction of the strike, and whether the gouge contains tool marks; cast the gouge. Check the hinge side for matching spread marks and the bolt tip and strike lip for fresh metal transfer. Establish whether the strike damage is old (corrosion, paint bridging) or fresh. Without those, hypotheses 1 and 3 both remain open.
2. Before anything is removed, what examination and documentation steps do you take, and how do you package the components?
Read the worked answer
In place, before handling
- Photograph overall, mid-range, and close-up with a scale: door position, gap measured, bolt extension measured, strike deformation, gouge, screw holes, paint fracture, thumbturn position.
- Record the thumbturn position photographically; it is ephemeral and any later handling destroys it.
- Do not cycle the lock, insert a key, or close the door. Note whether the bolt can be moved by hand.
- Cast the jamb gouge (e.g., Mikrosil or equivalent) before the frame is disturbed; this preserves potential tool marks.
- Measure and record screw-hole elongation and strike deflection with a caliper.
Collection
The deadbolt strike plate and both screws are separate items: they carry tool marks and hole-elongation evidence. The cylinder/bolt assembly is a third item. If practicable, take the door section or a cut-out of the jamb containing the strike mortise, because the relationship of plate to wood is itself evidence.
Packaging and chain
Package each item separately in rigid or padded containers, seal with tamper-evident tape, initial and date across the seal, and log every transfer. Photograph items again at intake before any disassembly. A locksmith examination that requires pin removal should be video-recorded and witnessed, and the pin stack documented before and after.
3. Write the opinion paragraph you would put in your report, including what you cannot say.
Read the worked answer
Model paragraph
The rear door was found ajar with the deadbolt fully extended. The deadbolt strike plate was deformed outward, both retaining screws were pulled from the jamb with holes elongated away from the door stop, and a lever-type gouge was present on the jamb face at bolt height with fresh paint fracture. This pattern is consistent with outward displacement of the door and jamb while the deadbolt was extended, a mechanism commonly produced by prying between the door and jamb. The damage is not consistent with the deadbolt having been retracted by a key or by cylinder manipulation, because the bolt remained extended.
What the report must also state
- No opinion on who caused the damage or on the time of entry.
- The homeowner's statement that the bolt was locked at 23:00 is her statement, not a finding.
- Alternative mechanisms (frame spread from inside, old damage subsequently aggravated) could not be excluded from the available examination.
- The cylinder face showed no defeat marks; that is absence of evidence, not evidence that no key or picking tool was used.
Use consistent with and disclose the alternatives tested. Do not write forced entry confirmed; the physical findings support a mechanism, not a completed offence.