Mechanism of injury (MOI) refers to the method by which damage or trauma occurs to the body (skin, muscles, organs, and bones). Now, this is where forensic nurses get to use those high school and freshman college physics lessons! Understanding MOIs and the resulting bodily insults requires combining a bit of physics with anatomy and physiology to determine the effect of the manner (type), direction, amount, and location of force applied to the body and the resulting injury/injuries.
Isaac Newton’s First Law of Motion states that a moving object will continue to move at the same speed until an opposing or outside force acts upon it. When this happens, the object’s kinetic energy is transferred to the outside object. For our purposes, the object is a weapon of some type, and the outside object is the body and this transfer of energy causes trauma or injury (typically, blunt/non-penetrating or penetrating). However, the transfer of energy can also be through a thermal agent such as heat, chemical, or cold agents and can also cause trauma to the body. This concept of the transfer of energy helps healthcare providers assess the likelihood and severity of injuries based on the nature of the incident and the Forensic Nurse Consultant to link (or not) the injuries to the indicted charges.
In forensics, determining the mechanism of injury (MOI) is crucial for understanding how an injury occurred, which can help in criminal investigations and legal proceedings. Forensic experts analyze the physical forces and mechanical processes that caused the injury to determine the nature of the incident (i.e. accidental, self-inflicted, self-defense, or an intentional violent act). For example, in cases of blunt force trauma, the MOI can help differentiate between injuries caused by falls, car accidents, or assaults. Similarly, in cases involving sharp force injuries, understanding the MOI can reveal whether the wounds were caused by knives, glass, or other sharp objects and the directionality and/or angle of entry.
More specifically, when evaluating a case, Forensic Nurse Consultants consider the following:
The nature of force applied to the body
The estimated amount of force applied to the body
The events leading up to the transfer of energy/trauma
Positioning, location, and movement of the assailant and victim
Physical capabilities of the assailant
General medical condition of the victim
Post-injury medical care (when and what) provided to the victim
MOI can be crucial in determining court cases for several reasons:
Establishing Liability
Supporting Evidence
Refuting or Confirming Defenses
Accurate Diagnosis and Treatment
MOIs are broadly sorted into several categories, based on the type and amount of energy transferred. Each has distinct characteristics and associated injuries.
Blunt
Penetrating
Ballistic
Acceleration/Deceleration
Thermal
Chemical
Electrical
Blast
Crush
Asphyxial
