INJURY CAUSATION AND CLASSIFICATION

• Jurisdiction: Australia

Introduction ................................................................................................... [33A.1400]

Abrasions ...................................................................................................... [33A.1410]

Bruises (contusions, haematomata and haemorrhages) .............................. [33A.1420]

Age of a bruise.............................................................................................. [33A.1430]

Special types of bruises................................................................................ [33A.1440]

Lacerations .................................................................................................... [33A.1450]

Incised wounds ............................................................................................. [33A.1460]

Superficial incised wounds............................................................................ [33A.1470]

Incised wounds of stab type ......................................................................... [33A.1480]

Interpretation of homicidal stab wounds ....................................................... [33A.1490]

Width of the blade......................................................................................... [33A.1500]

Length of the blade ....................................................................................... [33A.1510]

Nature of the blade ....................................................................................... [33A.1520]

The force used .............................................................................................. [33A.1530]

Distortions to the wound ............................................................................... [33A.1540]

Non-kinetic injury types Burns ............................................................................................................. [33A.1550]

Electrical burns .............................................................................................. [33A.1560]

[33A.1400] Introduction

Determining the causation of injuries may involve addressing several questions that are centred around injury classification:

1. What is the nature of the injury?
2. What type of object could cause the injury?
3. How could the object cause the injury?
4. When was the injury caused?
5. What was the nature of the force used to cause the injury? and
6. In what manner (accidentally, by assault or by self-infliction) was the injury or injuries caused?

The answers to the first five questions require medical knowledge of the classification and characteristics of the different types of injuries. The pattern of injuries observed on a body can frequently provide far more information on the final question than the appearance of any single injury. By "pattern of injuries" is meant an analysis of the number, type and distribution of injuries over the body. Expert forensic medical evidence is often needed to assist the court in coming to a conclusion, for example, as to whether the incident of injury infliction took place in a situation of accident, homicide or suicide. This is an area of opinion that is especially important in cases of suspected child abuse or otherwise inflicted injury, where any individual injury on the child could have an explanation consistent with an accidental mechanism, but when the overall pattern of injuries, and specific characteristic injuries are considered together, the opinion this case is one of child abuse and not of accidental injury becomes much stronger (refer to Part C -Paediatric forensic pathology).

Another classic example where this was of critical importance is in the Peden case.¹ In this 1922 case, a married woman was found dead in her bedroom with multiple deep incised wounds to the front of the neck (ie, a cut throat). The husband, who was unpopular with the wife's family, was arrested for murder on the basis of the medical practitioner's analysis which was concentrated on the injuries to the neck. He felt it was not possible for such injuries to be self-inflicted. Had he gone on to ask himself "In what manner?" (ie, question (6) above), he may have been moved to consider more carefully the total picture which included the absence of any injuries elsewhere. Usually homicidal cut throats are the coup de grace following a number of other stabbed and/or incised wounds. The absence of any other such injuries (plus a greater experience of the potential of severe neck wounds to be self-inflicted) is a major pointer to self-infliction. The consequences of the medical practitioner's analysis in this case were: (i) an inquest with an adverse finding against the husband; (ii) at the first trial, a hung jury; (iii) conviction at a second trial; (iv) appeal to the Court of Criminal Appeal lost; (v) appeal to the High Court lost; and (vi) release following consideration of "new" expert evidence at a Royal Commission. (Interestingly, these six steps took only 12 months.)

In summary then, to analyse the cause of injuries properly, there must be an understanding of:

1. the classification; and
2. the interpretation of the patterns of injuries.

It is essential that injuries are correctly classified because this immediately indicates something about causation. Correctly describing an injury can provide a more accurate reconstruction of the events that led to the injury. Leaving aside gunshot wounds (which are a special form of compound injury) and injuries associated with heat, cold, electricity and chemicals (burns), the common classification of injuries is abrasions, bruises, lacerations, incised wounds and stab wounds. The following classification is just one of many that can be found in standard forensic medical texts. It is important to remember that any classification is simply a way of drawing distinctions between different types of wounds and that in practice many wounds are compound in nature-that is, an admixture of several injury types.

----------

¹R v Peden (NSW Clerk of the Peace, Central Criminal Court, 9/7257); Molomby (1981, p 4ff); Cordner (1990); Pounder (1990).

[33A.1410] Abrasions

Abrasions are injuries that involve damage to the superficial layers of the skin. The word "abrasion" comes from the Latin words "ab", meaning "from", and "radere", meaning "to scrape". Strictly speaking, an abrasion should only injure the outermost layer of the skin, known as the epidermis. The epidermis does not contain any blood vessels, and as a result, technically abrasions damaging this layer should not bleed. However, the dermis, which is situated immediately beneath the epidermis, does contains blood vessels. If the dermis is injured, bleeding will occur. The interface between the epidermis and the underlying dermis is not smooth and pegs of outward-pointing dermis interdigitate with pegs of inward-pointing epidermis. As a result, a superficial scraping injury to the epidermis may damage some of the outward-pointing dermal pegs. This can result in a particular pattern of bleeding that may be seen in deeper abrasions. This pattern features a punctate or spot-like quality in the area at the bottom of the abrasion, reflecting the small pegs of injured dermis that contain blood vessels. Even deeper abrasions can be sustained, for example, where a person is dragged under a motor vehicle for some considerable disease, with resultant abrasion of tissue to such an extent that there may be exposure of bone and other organs of the body.

Abrasions can be caused after death, when their characteristics may be somewhat different. Post-mortem abrasions rarely bleed despite their depth. Because of the loss of the waterproof layer of the skin, they rapidly dry out to give a hard, pale yellow-orange, parchment-like characteristic to the affected area. Even ante-mortem abrasions will eventually show such parchment-like change after death as a result of the dermis drying out once it has been denuded of its water-resistant epidermis. Because of the surface bleeding or the underlying subcutaneous bruising that may have occurred in association with the ante-mortem injury, when the abrasion dries out after death, it often takes on a purple/black appearance. From a lay perspective, ante-mortem abrasions, when photographed or viewed some time after death, may take on the appearance of a more "severe" type of injury as a result of this drying and darkening of the injured skin. In extreme examples, and typically involving the scrotum, such drying of the skin can result in the appearance of artefactual abrasions where no abrasive injury had been sustained prior to death.

Although they may be associated with other injuries, including significant internal trauma, abrasions of moderate size are not usually serious from a medical point of view. Commonly, very minor abrasions not associated with bleeding may be ignored in a clinical setting, with the injury only visible as a small white skin tag. By contrast, even such minor superficial abrasions are often of considerable medico-legal importance as they may have a shape that suggests the nature of the object that caused them or provide information as the direction of the force involved.

Abrasions may be of particular forensic significance due to a number of their features. The pattern, shape and distribution of several types of abrasions are discussed below. With very few exceptions, abrasions occur at the site of application of blunt force, thereby giving invaluable information on the site of injury and often the nature of the object which caused the injury. Because an abrasion involves forceful scraping contact, there is a high possibility that foreign material will be transferred from the object onto the surface of the skin, where it may be held by surface fluids or blood. Gravel, paint flakes, wood, or glass fragments may be found over the surface of abrasions, as may be liquid contaminants such as paint or oil. Such material can often be recovered by swabbing...