Marks, Impressions and Physical Examinations
Physical fitting provides conclusive evidence of the previous union of two or more pieces:
- Broken fragments or pieces of metal, plastic, glass, ceramics, wood, paper, cloth, tape, paint chips, bone and teeth may present complementary broken edges or surfaces.
- The torn or cut end of duct, vinyl, electrical or other packaging tape can be compared with other strips or a roll of tape.
Physical examinations can provide information on source or origin:
- Newspaper sheets can be linked to a specific copy, based on random characteristics that arise during cutting of the newsprint.
- Plastic bags can be linked to a particular mass-produced batch or even placed in a specific sequence of manufacture.
- Examinations of ropes and knots can link a suspect or victim to a crime or unnatural incident.
- Manufactured articles of similar design and comparable gross and microscopic features.
Toolmarks and Manufacturing Marks
Tools such as hammers, crowbars, diagonal pliers, bolt cutters, screw-drivers, chisels, drills, etc are often used in the commission of crimes. Toolmark examination allows a questioned toolmark to be linked to a particular tool. Trace evidence on tools may reveal its history of use.
Commercial product packaging and security seals suspected to have been tampered with can be examined for evidence of tampering.
Bare footprints or footwear marks are generally present in a crime scene. Latent or faint marks and bloody impressions can be physically or chemically enhanced. No matter how incomplete or partial a shoeprint mark, forensic examination of these marks together with the shoe has the potential to uniquely link a specific shoe to shoeprints at the crime scene.
Tyre-prints and Vehicles
Sometimes, the only indication of how and when the criminal accessed or departed from a crime scene is a set of tyre-prints on soft soil. In hit-and-run incidents, tyre-prints may be left on clothing or skin of victims. Tyre-prints can be examined and associated to a specific tyre or to a class of tyres.
In traffic accidents, the undercarriage, body, wing-mirrors and other parts of the suspect vehicle may be examined for damages, removal of grime, contact patterns, fibres, human tissue, blood and paint smears. Examination of a lamp filament can reveal whether the lamp was incandescent (energised) when its glass envelope was broken or subjected to an impact force such as a vehicular collision. Obliterated stamped serial numbers on the engine block and chassis of stolen vehicles can be restored.
Cuts, Tears and Damage
Damages on fabrics can be examined to determine the freshness and the cause of the damage. In sexual assault cases, the nature of damages on clothing can reveal whether the act was consensual or forced.
Articles and materials that fail mechanically can be examined to establish the cause of failure: deliberate damage, wear and tear, chemical attack, mechanical failure or natural causes.
Firearms evidence is encountered in armed robberies and other crimes involving shooting, training incidents, suicides and accidental discharge. We examine and determine: muzzle-to-target distance, entry/exit holes, point of impact, gunshot residues, calibre and type of ammunition component, association of a bullet, cartridge case or shotshell casing to a specific firearm, and contact evidence (such as glass chips, paint and fibres) on bullets. We perform bullet trajectory analysis and shooting reconstructions.