Chapter Five (80-87) Knives and blunt Instruments

Chapter 5 HW Check 1.If the blood beneath a bruise contains high levels of white blood cells, what does this tell a forensic expert? (Q.5) 2.List the different colours a bruise changes to during healing. (Q.6) 3.What can prevent a downward blow of a knife from penetrating vital organs? (Q.9) 4.Name one piece of information that can be gathered by studying a stab wound. (Q.10) 5.Name one piece of evidence that would suggest to a forensic expert that they are dealing with a suicide. (Q.12)

1. Describe the types of crimes “crude weapons” may be used for as opposed to firearms: The use of firearms implies a degree of premeditation. Evidence can be left which ties the gun to its user and to the crime. Used in crimes that are unplanned. Stiletto Switchblade

Other Crude Weapons

2. Why are so many blunt instrument injuries delivered to the head area? Natural area of attack when swinging an object. Attacker believes they can do the most damage in this area.

3. What clues can be gained from examining these injuries? Shape of the injuries can reveal the murder weapon or at least its shape Site of injuries, such as fractures, can give clues of the victims positioning during the attack. Can also give clues of the height and strength of the attacker

Bruises A bruise is generally understood to mean an area of hemorrhage caused by the leakage of blood from ruptured vessels

Abrasions An abrasion or ‘graze’ is clinically only a minor injury, but may have forensic significance. It is a superficial skin injury which doesn’t generally penetrate the full thickness of the epidermis.

Types of Abrasion - Sliding When an object scrapes away a layer of skin “Road rash” is an example. Rope and other materials used for strangulation also cause sliding abrasions.

Types of Abrasion - Stamp When a blunt object strikes the skin, crushing it and leaving a raw area. May reflect eh general shape of the object that made it.

Types of Abrasions - Patterned Special type of stamp abrasion that leaves behind a pattern: – Chain, vehicle grill, pattern on clothing.

Lacerations Lacerations are tears caused by blunt force trauma. Lacerations are caused when a blunt object or surface impacts against the skin resulting in compression, crushing and splitting.

Skeletal evidence of blunt force trauma

4. How does bruising occur? Why might it be important to know the “patterns of bruising”? Bruises occur when blood vessels beneath the skin are broken. Can help piece together the order of events. Can also show where the fatal blow was struck. Can see if blood vessels broke before or after death. 5. Explain how white-cell count can give investigators valuable information? If a sample of blood found beneath a bruise has an abnormally high white-cell count, it suggests the bruise occurred before death.

6. Describe the changes that bruising goes through that helps determine time of injuries: Fresh bruise  appears purple or red in colour Progressively changes to brown  green  yellow

UBC Pediatrics

7. What can some non-fatal knife wounds tell a forensic investigator? Cuts to a victims hands and arms show attempts at self-defence. In cases such as this, the attacker can often become covered in the victims blood. If found, this proves the assailants role in the crime.

8. Describe the difference between incise wounds and stab wounds Incise wound  is a long, cut like wound, which is both plainly visible and will often bleed heavily. Stab wound  causes by a blade being pushed into the body of a victim. This can cause internal bleeding. When the knife is remove, the wound often shrinks and becomes less obvious.

9. When using a knife as a weapon, why is an upward blow usually more fatally effective than a downward blow? Upwards blows penetrate the chest wall between the ribs and can damage vital organs. Downwards blows normally glance off the rib cage preventing it from entering deep enough to cause major damage.

10. What information can be revealed from studying a stab wound? Width of blade is unreliable because it may have been moved while in the victim’s body. Know that length of weapon must equal at least depth of wound. Can determine if the knife was single or double edged.

11. What might a victim’s throat being slashed tell investigators? Because slashing a throat in an equal struggle is very difficult, it suggests that the victim was held down, tied up, or rendered unconscious before the injury was inflicted.

12. In point form, describe the clues that might allow investigators to determine if they were investigating a homicide or a suicide. Suicides involving knives usually include wounds to the throat, stomach or chest. One or two deliberate stab wounds with clothing removed = suicide. Multiple stab wounds, over wide area of body and threw clothing = homicide Right handed suicide to neck = a slash that starts high on the left side and continues to a lower spot on the right side. Can also be marked by one or two shallower gashes, which are “trial attempts”. Wounds to hand and arms also suggest homicide.

13. What were the THREE clues investigators came up with to determine that the case in England was a murder disguised as a suicide? Victim could not have possibly held onto a knife after the shock of a shot gun blast, unless rigor mortis set in immediately. Suspect had no defensive wounds on his arms and hands, despite suggesting he was in a struggle with the victim. The victims hand was covered in blood, which suggests he grabbed his chest after he had been shot, and had not, in fact, been holding on to the knife when he died.