Monitoring Window
47
minutes of RSSI data
Closest Approach
2.0 m
± 0.7 m · driver-side
Location Accuracy
4 m
radius confidence circle
Absence Window
18:18
min:sec · overlaps offence
Path Loss Exponent
n=2.7
outdoor/vehicle obstruction
— Event Timeline Overview —
RSSI Signal Strength over Time · Defendant's Paired Bluetooth Device
Spatial Reconstruction · GPS Anchor + Distance Rings
1
Phase 1 · Approach & Brief Presence
First Contact
20:47:32 → 20:55:47
Device detected at outer Bluetooth range (~100 m) approaching at steady walking pace (~1.3 m/s). RSSI strengthened from −91 dBm to peak −54 dBm. Bluetooth connection established automatically at 20:50:52 when device entered close range.
PEAK RSSI −54 dBm · 2.5 m ± 0.8 m
GEOMETRY Driver-side pavement approach
DURATION ~90 sec in close vicinity
2
Phase 2 · Critical Absence Window
18 Minutes, 18 Seconds
20:55:47 → 21:14:05
Zero Bluetooth signal. Device 100+ m from vehicle. Commercial premises (offence location) are 85 m NNE. The absence window exactly accommodates: walk to premises → time inside → return. CCTV timestamps corrected for 18-min clock drift align precisely.
LAST SIGNAL 20:55:47 · −95 dBm → lost
GAP Exactly 18 min 18 sec · no readings
PREMISES 85 m NNE · within absence radius
3
Phase 3 · Return & Departure
Second Approach
21:14:05 → 21:23:23
Device re-detected from eastern direction — same as northern commercial premises exit. Stronger peak RSSI than Phase 1 (−53 dBm vs −54 dBm), consistent with device at different orientation. Departure northward via alternate exit at brisk walk (~2.0 m/s).
PEAK RSSI −53 dBm · 2.0 m ± 0.7 m
DIRECTION Return from east · depart north
PACE ~2.0 m/s brisk walk on departure
FINDING 01
Passive Radio as Witness
The detachable head unit operated in standby Bluetooth scan mode while parked, engine off, panel removed. Every 30 seconds, the BT controller logged RSSI for all paired devices in range. No user action required — the vehicle was the witness.
Record Type 0x04 · Poll interval: 30s standby / 5s connected
FINDING 02
Absence Matches Offence Window
The 18:18 absence gap overlaps precisely with the offence window once CCTV clock drift is corrected. Two independent evidential streams — Bluetooth log and CCTV — converge on the same 18-minute period.
CCTV drift: +18 min · Corrected window: 20:56–21:14
FINDING 03
Driver-Side Geometry Confirmed
Both closest-approach arcs intersect on the driver-side pavement, 2–3 m from the vehicle. The GPS ring intersection eliminates the passenger-side and rear of vehicle as possible positions. Not a passer-by — a person accessing the driver's door.
4 m radius circle · GPS HDOP 1.1 · ±3.5 m anchor
RSSI_ref = −59 dBm at 1 m (manufacturer spec)
n = 2.7 (outdoor, partial metal obstruction)
Smoothing: Savitzky-Golay filter, window=5, poly=2