Evidence Register & Recording Characterization

Case FA-2026-001 | 4 cell phone recordings from the UVU shooting

EVIDENCE REGISTER

ID File Device Sample Rate Duration
R1 7_original.mov iPhone 16 Pro Max 48kHz stereo + APAC 4ch 161.3s
R2 IMG_2201.mov iPhone 15 Pro 44.1kHz stereo 36.8s
R3 IMG_6368.mov iPhone 15 Pro 44.1kHz stereo 7.3s
R4 IMG_9820.mov iPhone 15 Pro 44.1kHz stereo 69.2s

CHAIN OF CUSTODY — SHA-256 HASHES

R1: F6B375C5...694334
R2: 5103A730...A932F4
R3: A3DF1F4B...C70FAE
R4: 1D321FD8...02515C

Full hashes available in case file. Working copies derived from verified originals.

RECORDING CHARACTERIZATION

R1 7_original.mov NO AGC
Device: iPhone 16 Pro Max
AGC suppression: 0.2dB — amplitude ratios reliable
Spectrum: 83% energy in 1–5kHz (mid-frequency dominant)
Mach cone: No precursor detected
Rise time: 5.17ms (fastest)
Reflections: +95.5ms (−2.5dBFS), +164ms, +389ms
SPATIAL AUDIO — APAC PENDING

R1's iPhone 16 Pro Max recorded a 4-channel APAC (Apple Positional Audio Codec) spatial audio stream alongside the standard stereo AAC track. This is 1st-order ambisonics: 4 spherical harmonic components (W omnidirectional + X front-back + Y left-right + Z up-down).

The APAC stream could provide direction-of-arrival (DOA) information — an independent cross-check on the TDOA solution that does not depend on multilateration.

Currently undecoded: APAC requires Apple hardware (macOS AudioToolbox framework) to decode. FFmpeg 8.0 detects the stream but cannot decode it. VLC produces only 2 of 4 channels. Awaiting decode on Apple hardware.

R2 IMG_2201.mov AGC ACTIVE
Device: iPhone 15 Pro
AGC: Active — only arrival times forensically useful
Position: Near/against building wall
Wall reflection: Early at +50.1ms (−3.3dBFS)
Reflections: +50.1ms, +216ms, +342ms
R3 IMG_6368.mov AGC ACTIVE
Device: iPhone 15 Pro
AGC: Active — only arrival times forensically useful
Duration: 7.3s (shortest recording)
Onset: Clean onset, high confidence pick
Spectrum: LF-dominant
Reflections: +111ms (−7.5dBFS), +201ms
R4 IMG_9820.mov AGC ACTIVE MACH CONE
Device: iPhone 15 Pro
AGC: Active — only arrival times forensically useful
Mach cone: 18× precursor in 4–6kHz — strong detection
Trajectory: R4 is DOWNRANGE of bullet trajectory
Rise time: 26.99ms (slowest)
Reflections: +53.8ms (−3.6dBFS), +247ms, +259ms

ENVIRONMENTAL CONDITIONS

Temperature 85°F (29.44°C)
Humidity 37%
Elevation 1404m
Atm. Pressure 855.6 hPa
Speed of Sound 349.7 m/s (Cramer 1993)
Sensitivity ±2°F → ±0.7 m/s → ±0.58ms per 100m

RECEIVER POSITIONS

Origin: Stage center at 40.27758°N, 111.71395°W, ~1404m elevation. X = East, Y = North.

Receiver Latitude Longitude Local X (m) Local Y (m)
R1 40.27766021 -111.71408670 -11.59 +8.91
R2 40.27744771 -111.71401341 -5.38 -14.70
R3 40.27745211 -111.71400892 -5.00 -14.21
R4 40.27744234 -111.71386567 +7.15 -15.30

R2–R3 separation: 1.6m. R1 is the only receiver north of stage. Array spread: 18.6m E-W × 24.1m N-S.

PA SPEAKER ARRAY

EV Everse 12" battery-powered speakers, daisy chained, no inter-speaker delay. Directionality facing NE (~66° bearing).

Speaker Latitude Longitude Local X (m) Local Y (m)
S1 40.27748964 -111.71397234 -1.89 -10.04
S2 40.27751622 -111.71399493 -3.81 -7.09
S3 40.27754732 -111.71401988 -5.93 -3.63
S4 40.27756383 -111.71406273 -9.56 -1.80
S5 40.27780757 -111.71408487 -11.43 +25.29

S5 is a distant delay/monitor speaker — excluded from PA correction models.

REFLECTION STRUCTURE

Receiver 1st Reflection 2nd 3rd
R1 +95.5ms (−2.5dBFS) +164ms +389ms
R2 +50.1ms (−3.3dBFS) +216ms +342ms
R3 +111ms (−7.5dBFS) +201ms —
R4 +53.8ms (−3.6dBFS) +247ms +259ms

Reflection delays are measured relative to the direct arrival at each receiver. R2's early +50.1ms first reflection is consistent with its proximity to a building wall, producing a short-path specular reflection. Reflection arrival times can be used to verify the solved source position against known building geometry — comparing predicted reflection path lengths with measured delays provides an independent cross-check on the TDOA solution (pending future work).