Forensic Analysis of Sharp Force Trauma Wounds
Wounds Caused by Cutting Instruments
Wounds caused by cutting instruments are defined by the existence of a thin blade and a triangular section edge (_filo_). True cutting instruments include: knives, razors, scalpels, etc.
Mechanism of Action
The edge penetrates the tissue like a wedge, dividing it and producing solutions of continuity.
Characteristics of Incised Injuries
Incised injuries typically fall into three types: linear wounds, flap wounds, or wounds resulting from oblique penetration.
Linear Wounds
The instrument enters perpendicular to the skin, producing a simple solution of continuity. The open wound is elongated and oval, resembling a true surface scratch. Distinguishing characteristics include:
- Edges: Incised wounds are characterized by the regularity and cleanliness of their edges. When retracted, the wound takes on a fusiform shape.
- Ends (Tails): Wounds often become superficial at the ends, forming what are called “queues” (tails). This is more apparent when a slip mechanism predominates. There is an “attack tail” at the start of the cut and a “terminal tail” at the end.
- Walls and Depth: The depth results in the formation of two walls that are smooth and regular. There are never substance bridges linking the walls.
Flap Wounds and Oblique Penetration
When the cutting tool penetrates more or less obliquely, one edge forms an obtuse bevel cut, while the other creates a foil or flap of triangular section with a thin free edge. The size and thickness of this flap vary depending on the weapon’s length, the obliquity of the cut, and its depth. Flap injuries occur when the [text ends abruptly here, but the description above covers the mechanism].
Atypical Incised Wounds
Atypical incised wounds include:
- Erosions or Grazes (_Rozaduras_): Caused when the instrument merely touches the skin tangentially, resulting in an erosion or partial detachment of the epidermis.
- Zigzag and Bridge Wounds: These are due to the characteristics of the skin or region, often occurring where loose skin forms folds easily (_pliegues_).
- Irregular Wounds: These are modified forms of incised wounds resulting from a lack of sharpness on the weapon’s edge or the existence of dents.
- Mutilating Injuries: Occur when the instrument attacks a salient part of the body. If the weapon is very sharp, these injuries often involve traction or avulsion mechanisms.
Classification of Sharp Instruments
The damaging part of these instruments consists of a blade, more or less tapered and narrow, crossed by one, two, or more sharp, cutting edges. Instruments are classified by the number of edges:
- Monocutting (one edge)
- Bicutting (two edges)
- Pluricutting (multiple edges)
Sharp instruments frequently encountered in medicolegal practice include: knives, utility knives, daggers, stilettos, etc.
Characteristics of Stab Wounds (Puncturing Injuries)
A stab wound consists of a canal that runs through the various tissues involved in the injury. A characteristic feature is that the direction of the wound opening (the “eye”) that forms at the outlet is often different from the inlet.
The outlet is usually more irregular than the input, and atypical fissures and cracks may occur. Its size is generally smaller than the inlet.
Prognosis and Forensic Considerations
The prognosis depends on several factors:
- Instrument characteristics (fineness of edge, cleanliness of the weapon).
- The wound area and depth of injury.
- Thickness of the instrument (relevant for stab wounds).
Severe bleeding (hemorrhage) is constant in these types of injuries. The wound may be fatal depending on the area affected. Healing of incised lesions is usually rapid, resulting in linear or elliptic scars, more or less elongated.