Tungsten Trioxide (WO3)
Definition
Pale yellow oxide of tungsten formed rapidly at temperatures above approximately 800 K when tungsten is exposed to atmospheric oxygen; its presence on a fractured filament is the primary physical indicator of hot-filament failure.
- Appearance
- Pale yellow oxide
- Formation temperature
- Above approximately 800 K
- Formation condition
- Tungsten exposed to atmospheric oxygen
- Forensic significance
- Primary physical indicator of hot-filament failure
- Context
- Vehicle headlight filament examination
Common questions
How does the presence of WO3 help determine whether a headlight was on at the moment of impact?+
The oxide only forms rapidly at the high temperature the filament reaches while glowing, so its presence on the fractured ends indicates the filament was hot and the light was illuminated at the time it broke, distinguishing that from a cold, unlit filament that snaps cleanly without oxidation.
What does the absence of tungsten trioxide on a broken filament suggest?+
It suggests the filament was cold when it fractured, meaning the light was likely off at the moment of the break, though an examiner still considers other fracture characteristics such as stretching or beading before concluding the bulb's operating state.
Related terms
- ASTM E2927
- Standard test method for the determination of trace elements in glass samples using LA-ICP-MS; specifies the element suite, calibration standards (NIST SRM...
- BNS 2023 § 106
- Bharatiya Nyaya Sanhita 2023 provision criminalising causing death by negligence; the primary charging provision for fatal hit-and-run cases in India, with enhanced...
- Cold Filament Failure
- Fracture of a tungsten bulb filament below operational temperature; characterised by a clean, brittle transverse fracture with no deformation and no oxide...
- EUCAP
- European Collection of Automotive Paints, maintained at the Bundeskriminalamt (BKA) in Wiesbaden; the European counterpart to PDQ for automotive hit-and-run paint comparison.
- FCIN
- Forensic Collision Investigation Network (UK); provides standardised protocols for fatal and serious-injury collision forensic examination, including paint, glass, tyre and filament examination.
- Hot Filament Failure
- Fracture of a tungsten bulb filament while at operational temperature (2,500-3,000 K); characterised by ductile deformation at the break, coiling, and tungsten...
- LA-ICP-MS
- Laser ablation inductively coupled plasma mass spectrometry; a technique that fires a laser pulse at a sample surface, vaporises a tiny amount,...
- PDQ (Paint Data Query)
- RCMP-maintained international automotive paint database. Stores binder, pigment and layer data for vehicle original-equipment finishes from major manufacturers. Used to narrow a...
- PVB Interlayer
- Polyvinyl butyral film bonding the two glass layers in a laminated automotive windshield; retains broken glass in place after fracture, preserving the...
- SWGTREAD
- Scientific Working Group for Shoeprint and Tire Tread Evidence; US body that developed the dominant guidelines for footwear and tyre-mark examination, class-subclass-individual...
- Treadmate
- RCMP database of outsole designs for footwear comparison, used by Canadian forensic laboratories and accessible to partner agencies.