In every physical assault, no matter it led to death or not, the attacker will produce/leave different types of marks in the victim's body that will guide to reconstruction of the crime scene and will help to determine the cause of death.

Every type of weapon will produce a characteristic injury. In the case of knife stabs, we will find mostly internal injuries and consequent haemorrhages; while in knife slashes, if these are directed to main blood vessels, the effect can be as equally lethal. Lastly, the use of a blunt instrument such as a hammer, a rock or a baseball bat will brake bones, damaging internal organs, possibly producing death but always leaving superficial marks on the flesh.

B R U I S E S · C O NT U S IO N S :

Bruises or Contusions are caused by blunt trauma injuring the tissues and resulting in damage to blood vessels beneath the surface. Blood leaks out ('extravasation') into surrounding tissues from damaged capillaries, venules and arterioles. The resulting bleeding may be petechiae: pinpoint bruises, usually due to venous engorgement, for example in asphyxia, or in defects in blood coagulation such as Disseminated Intravascular Coagulation (DIC) than trauma; Ecchymoses - smaller than a few milimeters; and Haematoma: larger than the previous.

Contusions are among the most relevant physical injuries to the forensic pathologist, helping to determine points of instrument impact; force applied, and estimated time.

Probably the most important fact to highlight about bruises is that they can only be inflicted on a living person, cause there will be lack of circulation after death. All the same, a great force applied on a corpse will resemble bruising, but this won't be anything in comparison to the ones produced on a living person and would be soon revealed on an autopsy.

Also, the extent to which a person bruises depends on the age, gender area of impact and possible diseases. For example, older people will get bruises more easily than young people, the same as women in relation to men. Of course, the presence of an underlying disease as haemophilia, liver diseases, and alcoholism will also be of importance in the interpretation of bruises. D ifferent parts of the body are more susceptible to bruising than others. For example, the skin over the eyelids bruises easily, whilst the tougher palmar surface or plantar surface rarely bruises  

Unlike abrasions, the characteristics of the object causing a contusion cannot easily be determined. The leaking blood usually tends to diffuse through the tissues, following the layers underneath the skin, along facial planes. An important phenomenon to bear in mind is the apparent 'shifting' of bruises after time. For example, a scalp injury may result in a black eye and bruises may also 'appear' after some days due to the same reason. For this reason, pathologists often re-examine a body again to look for such bruising.

However, there is an exception to this. Intra-dermal bruises, as they occur in the upper-most layer of tissue, lying just under the epidermis may reproduce the pattern of the causative object, for example the tyres of a car or the pattern on a belt. Beating with a a smooth thin rod often produces ‘tramline' bruising: two parallel lines caused by the sides of the rod, rather than by the direct blow. The blood vessels under the point of impact are squeezed by the blow and emptied of blood, while those on either side rupture. A similar phenomenon is seen when the injury is caused by a hard spherical object, such as a squash ball.

The time of the injury  

Due to degradation of haemoglobin in the blood, contusions change colour over time, switching from red to dark blue, brown, green, yellow till it finally fades. However, the timescale of this degradation is not fixed, cause even two bruises in the same person will change colours at different rates, making impossible the determination with any accuracy.  

Usually, bruises can take from 4 days to one week to fade out on a healthy person. But it is important to remind the if a bruise is brown/ green or yellow it is likely that the injury is at least 18 hours old (See the American Journal of Forensic Medicine and Pathology 16:203 (1995)).

Also, if there are multiple bruises on the same person, in widely different stages of the colour spectrum, this might suggest that they have been caused at different times, and may indicate signs of chronic abuse.

Type of the assault and the cause and mechanism of death

In forensic autopsies, it is important that all possible signs of trauma are specifically looked for and excluded. This includes a thorough search for bruising, including that which is beneath the skin surface. Forensic pathologists use specialist dissection techniques to expose deeper structures, and this may entail removing all skin off whatever structure is being looked at.

In cases of strangulation, bruises cause by fingers in the neck may be faint and small; but they can also much larger than the pads of the fingers of the assailant. Bruises must be looked   for in deep neck muscles.

When the shoulder blades show bruising, it may indicate that the body was pressed against a hard surface; and when these are located in the arms, they may show that the victim was being restrained.

Rape victims usually show contusions in the inner parts of the thighs, vulva, face, and arms.

And there is one last case of bruising called the ‘love bite', caused by suction rather than pressure. This type can be also find in sexual assaults in neck, breasts, etc.

L a c e r a t i o n s

These wounds are the result of skin split by the strength of a blow, commonly known as 'gashes, tears or cuts' of the skin. The force causes the full thickness of the skin to be damaged. Lacerations therefore bleed profusely. The tissues at the edge are grazed and bruised, and the split is irregular, with strands of nerve tissue and blood vessels stretching across it. However, scalp lacerations sometimes resemble incised wounds when they have been caused by a regular shaped object.

Lacerations generally appear in bony parts of the body, such as the scalp and above the eyebrows. And a blow form a metal rod can produce a y-shaped wound or less often, multiple lacerations as a result of one single hit.  

On the other hand, blows to lower parts of the body may not lacerate the skin, but cause extensive laceration of the soft tissue beneath.

K n i f e · W o u n d s

Incised, slashed and stab wounds are different types of wounds produced by knife or any other sharp element. An incised wound is a superficial wound in which the size of the wound on the surface is larger than the depth of the wound.   The edges will vary according to the nature of the cutting edge of the object, in that a razor will leave regular margins, whereas an axe may leave the wound margins crushed and bruised, resembling a laceration.

In Slash wounds the length is greater than the depth, e.g.

a slice wound across the skin. If the wound involves major blood vessels, it can be life threatening, but in general, they are not as serious as stab wounds.

And Stab wounds are those where the depth of injury is greater than the length. They penetrate more deeply than slash wounds and tend to come into contact with vital organs in the chest and abdomen.

Stabs are usually slit-like, but when the object is removed the skin contracts slightly, leaving a wound that is slightly shorter than the blade width. The centre of the wound often widens muscle and skin contracture around the wound often obscures the size of the knife blade. The size of the wound depends upon the depth of penetration of the knife, and whether, for example the parallel section of the knife has been reached (ie near to the hilt of the knife).

The depth of the wound is often longer than the length of the knife because of the compressibility of skin and underlying structures, particularly in the abdominal cavity.  

Scissor stab wounds (closed scissors) leave a 'Z' shape

It is important to remember that there are cases in which death has been caused by other means, like strangulation, and stabs were made post mortem. In these cases, the amount of blood coming out of the body will be considerably less.

The self-inflicted wounds as a suicide intend are likely to be clean cuts, because the individual usually throws back his or her head, stretching the skin.   

B i b l i o g r a p h y :

“Bodies of Evidence” – Brian Innes – Reader's Digest USA 2000

http://www.dundee.ac.uk/forensicmedicine/Crimes_against_Women_and_Children/D9-Traumatology.pdf

http://www.forensicmed.co.uk/index.htm