Types of Injuries Return to The Crime Lab Start with the Black Knight video http://www.youtube.com/watch?v=dhRUe-gz690 and the Tale of Sir Robin http://www.youtube.com/watch?v=c4SJ0xR2_bQ&playnext=1&list=PL3F8E90CCD4F9166C

There are many types of injuries that are possible, but it is important to remember the three most important factors in categorizing injuries: location, location, location!  If that sounds flippant, let's explore a few ideas:

1. First of all, the location (as in the organs involved) of an injury can, of course, determine whether or not it was the fatal injury.

2. Second, the location (as in depth) of an injury can help determine the severity of the injury, and the severity of the crime.

3. Third, the location (as in the location on the victim's body when it was in motion) of an injury can determine the nature of the interaction between the attacker and the victim.

In terms of the organs involved, for example, a gunshot wound need not be fatal.  A wound to the chest may provide only a temporary injury, whereas a wound to the arm could be fatal if a major artery is severed.  A person may be stabbed multiple times in the back or the abdomen and survive, but a single stab would to the heart would be fatal.

In terms of the depth, some injuries are only to the skin, such as bruising or lacerations, whereas a bruise to the skin can also involve broken bones.  A bruise on the temple could crack the cranium, thus leading to bleeding in the brain, and death.  Depth can thus give a great deal of information about the nature of the crime itself.

In the picture above there are five injuries to the skin that involve quite different scenarios:

1. An abrasion involves the scraping of the skin on a rough surface, usually from either a fall, or from a body being dragged.

2. An incision is a sharp cut with very clean edges, usually involving a sharp blade, as in a knife or scalpel.

3. A laceration, on the other hand, is a cut that involves rough edges.  This type of injury might be caused by the tearing of the skin by, say, the claw portion of a hammer, or claw marks from a large mammal.

4. A puncture is the penetration of the skin my a sharp object.  This is often something pointed, such as a thumbtack or an ice pick, or it can be something not so sharp, such as a fence post.

5. Lastly, and somewhat more unusual, is an avulsion, which involves a chunk of the skin being removed.  This type of injury often involves shrapnel from an explosion; the speed of the flying fragments can literally tear a portion of the skin off.  The nature of the injuries can thus say a lot about the location of the explosive device.

Note: Injuries 3, 4, and 5 above are reason enough why it is, how should I say it, oh yeah, stupid to lash yourself to a tree during a hurricane.  The expression "a little wind never hurt anybody" fails to take into account what is being carried by the wind: branches, boards, Buicks . . .

In terms of the victim's body when it was in motion, there is a great deal to be learned from this.

The nature of the internal injuries from a bullet will say a lot about the type of gun used.  A cavity is formed by the path of the bullet as it travels through the body, whether or not the bullet actually exits.  The formation of the cavity is called cavitation.

The speed of the bullet depends on the amount of gun powder in the cartridge.  Cavitation can be either temporary or permanent, with the largest permanent cavities being formed by the highest speed bullets:

It is important to note that the temporary cavitation involves the rapid rebound of the tissue after the bullet passes through the body.  Even though temporary, the damage from compression and subsequent stretching of the surrounding tissues can be permanent.  Note the location of the Kidney in the diagram above (it is just bean-shaped, in fact kidney bean-shaped, organ  medial to the entrance wound).  In the low speed handgun, the cavitation completely misses the kidney.  The rifle, with more powder in the cartridge, creates permanent cavitation that damages a small portion of the kidney.  The military ordinance, which uses a full metal jacket (notice the lack of deformation in the bullet itself), has far more powder in the cartridge, and thus far more energy!  The permanent cavitation is roughly equal in size to that of the hunting rifle, but the even larger temporary cavitation destroys most of that same kidney!

Note the Entry and Exit wounds in the skull above. 
The large hole you see in the left orbit (eye socket) is due to:

• the delicate nature of the bones of the skull, and

• the cavitation caused by the bullet itself

The following is an example of healed bullet wound injuries (both entry and exit wounds) from the civil war era.

For those of you who have had to deal with the learner's permit exam at the DMV, you are well aware of the seatbelt law.  The image below shows some of the injuries that can be sustained when you are NOT wearing a seatbelt.

Don't forget that you are moving at the same speed as your vehicle.  Inertia -- An object at rest will stay at rest, and an object in motion will stay in motion, unless acted upon by a force -- will force you, upon hitting another car, a lampost, etc., to continue at the speed of the car prior to the sudden stop.  Something, some force, will stop you: an airbag, a seatbelt, the dashboard, the windshield, the pavement . . .  (NOTE: As airbags now run on an electronic switch rather than a mechanical switch, and as we know, electronics never falter -- cough, cough -- it is ALWAYS a good idea to have a seatbelt buckled as well.  As a matter of fact, it's not just a good idea, it's the law!)  As long as we are on the topic, what's the likelihood of hitting something when you are talking on a cell phone while driving?  What about when you are texting while driving?  The best thing for you to do is to use your head, for if you don't the pavement will . . .

Beyond all of this, it is important to remember that the body reacts to injuries.  A severed artery or vein will bleed out, although at different rates.  A blunt trauma will cause bruising.  A broken bone will start to heal.  This, however, is only if the injury happens while the body is alive.  In some cases, the body will continue to receive trauma, long after it is dead.  The nature of the injury, and the body's reaction to it, determine whether or not the injury occurred antemortem (before death), perimortem (at the time of death), or postmortem (after death).  Once again, this says a lot about the nature of the crime itself.  Thus there is a fourth location that is important in terms of injuries, and that location involves the fourth dimension: TIME.

That is the subject of our next lesson.