Forensic Science
The injuries from blunt force trauma versus sharp force injuries have differences that help the investigator differentiate the type of the injury. Blunt force can create such injuries as abrasions, contusions, lacerations, and fractures of the skeletal system. Injuries from a blunt force trauma frequently have a bridging tissue, while sharp force injuries tend to lack it. Stab wounds are more common for sharp force injuries and should never be used as a synonym for laceration (DiMaio & Dana, 2006).
It should also be noted that sharp weapons produce a regular, linear wound, while blunt force traumas are often present in the form of abrasions; antemortem abrasions are reddish-brown, while post-mortem abrasions are yellow or translucent. There are different types of abrasion: scrape abrasions (on an epithelial layer or deep in the dermis), brush burn abrasions (scraping injury that covers a large body area), pressure abrasions (the skin is crushed), and patterned abrasion (a pattern of the object remains on the skin).
Contusions are also more common for blunt force traumas, although it does not mean that they are present only due to blunt force. Contusions might emerge during stab wounds as well; they are mostly produced by the guard of the knife if the stabbing was conducted with great force (DiMaio & Dana, 2006; Gad, Saber, Farrag, Shams, & Ellabban, 2012). Sharp force injuries include stab wounds, incised wounds, and chop wounds; such wounds often lack bridging tissue within the depth of the wound.
Chop wounds often lead to a groove or cut in the bone. It should also be noted that blunt force injuries might produce less severe damage to internal organs than penetrative wounds, although not always (Sharma, 2012). One should also remember that dull-edged chopping weapons can cause crushing of the tissue and result in a laceration.
Types of Injuries
Blunt force traumas are created by a blunt object that strikes the body or by an impact of a body against a blunt object/surface. While abrasions usually can heal without scarring and depend on various factors such as the medical state of the victim, the severity and location of the injury, contusions (bruises) may be present both on the skin and within internal organs. Deep contusions are not visible instantly and can appear hours after infliction (DiMaio & Dana, 2006).
Lacerations are caused by blunt force injuries, and the tissue might be stretched, crushed, sheared, or avulsed; they frequently occur over bony prominences. Long and thin objects produce linear lacerations, while flat objects cause Y-shaped lacerations. It is also possible to notice combination injuries that consist of abrasions, lacerations, and contusions. Blunt force can also cause skeletal injuries (e.g. chest injuries) and damage the internal organs that might not be indicated by any external injuries and damages; the lack of abrasions, contusions, lacerations, and fractures does not explicitly indicate that internal organs are intact.
Skeletal trauma analysis can also be complicated despite the extensive research and data on bone trauma (Passalacqua & Fenton, 2012). Chest injuries might result in rib fracture, cardiac injuries, aortic injuries, diaphragmic injuries, respiratory tract injuries, etc.
Blunt force can also lead to injuries to the abdomen, genitalia, extremity injuries, head, and neck injuries as well. Skeletal fractures can result in the focal, crush, penetrating, traction, angulation, rotational, vertical compression, vertebral column, pelvic fractures. Extremity injuries can be superficial (skin and subcutaneous tissue) or deep (reaching to muscles, bone, nerves, etc.). Upper extremity injuries can be of two types: defense (contusions and abrasions of forearms, upper arms, fingers/fingernail fractures) or offensive (abrasions, contusions of knuckles, metacarpal bones’ fractures) (DiMaio & Dana, 2006).
Sharp force injuries include stab wounds, incised wounds, and chopped wounds. Stab wounds do not have a bridging tissue and consist of a visible skin wound and an inner wound. Stab wounds are divided into three types: homicidal, suicidal, and accidental. Incised wounds are usually not fatal because the length of the wound on the outer level is greater than the depth of this wound. Such wounds also normally do not have bridging tissue. Chop wounds are caused by instruments with a sharp cutting edge, e.g. hatchets, axes, machetes, etc. A tangential chopping bow can cut away a disk-shaped portion of bone and/or skin (DiMaio & Dana, 2006). Soft tissue hemorrhage indicates that the wound occurred prior to the victim’s death.
Wounds Caused by Sharp Objects
Sharp weapons usually produce a regular, linear wound; a single-edged weapon can have a blunted margin and a V-shaped margin. Usually, single-edged weapons are used more often compared to double-edged ones (Savakar & Kannur, 2015). Scissors can produce linear or paired wounds, which depends on the way the stabs were made (with closed or open scissors). The margins of the external skin wound, if the injury is caused by a double-edged weapon, can be V-shaped.
A screwdriver can cause a circular wound, while a serrated knife can lead to a sawtooth cut on the skin of a victim. The level of penetration of the object into the body of the victim can also lead to different types of wounds. For example, superficial, mid-level, and deep penetration will have various forms of skin wounds with different margins (square or oval). Suicidal stab wounds usually differ from homicidal ones unless the victim was aiming to simulate homicide (Austin, Guddat, Tsokos, Gilbert, & Byard, 2013).
References
Austin, A. E., Guddat, S. S., Tsokos, M., Gilbert, J. D., & Byard, R. W. (2013). Multiple injuries in suicide simulating homicide: Report of three cases. Journal of Forensic and Legal Medicine, 20(6), 601-604.
DiMaio, V. J., & Dana, S. E. (2006). Handbook of forensic pathology. Boca Raton, FL: CRC Press.
Gad, M. A., Saber, A., Farrag, S., Shams, M. E., & Ellabban, G. M. (2012). Incidence, patterns, and factors predicting mortality of abdominal injuries in trauma patients. North American Journal of Medical Sciences, 4(3), 129-134.
Passalacqua, N. V., & Fenton, T. W. (2012). Developments in skeletal trauma: Blunt-force trauma. A Companion to Forensic Anthropology, 3(1), 400-411.
Savakar, D. G., & Kannur, A. (2015). A genetic algorithm and Bayesian approach for identification and classification of weapon based on the stab wound patterns caused by different sharp metal. Int. J. Comput. Eng. Appl, 9(1), 1-12.
Sharma, A. K. (2012). Management of pancreaticoduodenal injuries. Indian Journal of Surgery, 74(1), 35-39.