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Do let me remind you again that you're still at Question 1.
Today, let's take a look at bitemarks on victims. What are bitemarks?
Do let me remind you again that you're still at Question 1.
Today, let's take a look at bitemarks on victims. What are bitemarks?
“It
can be defined as a pattern produced by human or animal dentitions and
associated structures in any substance capable of being marked by these means
(Clark 1992)."
So what about “love bite” or “hickey”???? Well, that falls
under the same category too! It is said to be diagnostic of a human bite (Clark
1992) and are also known as suction marks.
Besides that, there are also reverse bites! These marks are
imprinted on the skin by the teeth during punching. Not only that, there are
also self-inflicted bitemarks that could be caused by a fall onto the face or
during an epileptic fit.
Now, let’s visualize this.
Have you ever imagined yourself in a perilous situation
whereby you have to fight off an attacker? You are all by yourself, equipped
with no weapons and in most of situations, I bet you would be in total shock or
frightened to even do anything! So tell
me, what will you do to fend off the attacker? In a life or death situation,
the human teeth are frequently used as a weapon! Indeed, it is fascinating to
use one of God’s creations in situations like these that could end up saving
our lives. Inflicting injury on an attacker using our teeth at times may be the
quickest and only available self defence technique, other than running away as
fast as lightning!
Now, let us look into bites caused by humans. We will
discuss about animal bites later.
HUMAN
BITES
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Figure 1 : Prototypical human bitemark
Picture adapted from : http://www.nature.com/bdj/journal/v190/n8/pdf/4800990a.pdf |
Assailants in sexual attacks which include sexual homicide,
rape and child sexual abuse are cases whereby the attackers would often bite
their victims to show that they are stronger or more dominating, to vent out
their anger and to express animalistic behaviour. On the other hand, victims bite their
attackers naturally to defend themselves. Children also bite each other! In
most cases, it is quite natural as they do this mostly to express anger or
frustration.
At the moment, the forensic dentists or forensic odontologists
have not come to an agreement on the individuality of the dentition or
behaviour of human skin during biting as these issues have never been proven
scientifically. Fortunately, there are researches which are currently being
carried out to prove the existence of the fact. As you should know, the sizes,
shapes and patterns of the biting edges of the front (anterior) teeth on the
upper and lower jaws are said to be different and unique for each person. This
is primarily due to the emergence or eruption sequence of the teeth. For this
reason, we are able to identify the attacker through bitemarks using proper
scientific techniques and also find more evidences to give us a clearer picture
on what had actually happened or taken place.
TYPICAL
PRESENTATION OF BITEMARKS
Bitemarks can be found on almost every part of the body. For
females, the breasts and legs are the common sites where you can locate bitemarks .
These usually happened during sexual attacks. Males differ from females where
the bitemarks are commonly found on arms and shoulders.
BITEMARK
MORPHOLOGY
“ According to Knight 1996 and
Clark 1992, bitemarks can be considered to be a spectrum of injuries ranging
from a suction mark, through marks indicating increasing violence ranging from
bruising with no indentations to deep lacerations made by penetrating teeth."
A human bitemark is generally circular, elliptical or oval
in shape bruise. Under that shape, they may have a doughnut-like shape with
characteristics record around the perimeter of the mark or it can be two
U-shaped arches with an open space at the bases of the arches. The diameter of
the injury is usually from a range of 25 to 40mm. You can also find a central bruising within
the marks in most cases and this is due to the extravascular bleeding when the
teeth applies pressure which compresses the tissue inward from the perimeter of
the mark. Furthermore, you can identify
specific types of teeth based on the marks. For instance, canines produce
triangular injuries whereas incisors produce rectangular injuries.
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Figure 2 : Range of bitemark severity
Picture adapted from : |
ANIMAL
BITES
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Figure 3 : Dog bite. Notice the pattern is different from a human
bite.
Picture adapted from : |
Now, you’re almost a step closer to becoming an expert in
analysing bitemarks. We shall go through quickly on animal bites. Who knows,
the killer could be a dog!
Animal bites such as dog bites or wild animals’ bites (bears,
lions) are different from each other and of course, very different from a
human’s. Hence, it is good to know about animals’ dentitions and the shape of
their arches.
In dog bites, the front (anterior) segment of their dental arch is
narrower compared to a human’s and displays a U-shaped appearance. Human’s
dental arch is rounded. The dog’s canine is more conical, curved and of course
larger. These small and fined details can definitely help you to find out which
animal bit the victim.
Why do they bite? Mostly, it is due to territory reasons and the
nature of the animal’s behaviour.
EVIDENCE
COLLECTION
Now, it’s time for you to place yourself in a laboratory or
clinical setting. What are your actions when you have a victim with a bitemark
injury before you? What steps are important? Let’s find out!
Firstly, remember either one of the mnemonics below:
Diablo
Play Station Is Fun or Dental Private School Is Fun (DPSIF)
1. Documentation
Conduct a history taking session first. Then,
document the injury and make important notes of the physical appearance,
colour, size and orientation of the injury. Ask necessary questions to find out
more about the bitemark.
2. Photographs
Take photographs of the injury using an
intra-oral camera with a macro lens and both colour and black-white film. Use a
ruler as reference scale and make sure that the long axis of the lens are
placed perpendicular to the injury.
3. Saliva swabs
Double swab tecnnique. First, use a moistened
cotton swab containing distilled water to wash the surface contacted using
light and circular motions, then a second swab to dry the remaining moisture on
the skin. These swabs will be collected and more tests will be conducted to
find out more about the saliva whereby you can find DNA evidence.
4. Impressions
Precise impressions are needed to study the
casts of the teeth. Dental impression materials such as vinyl polysiloxane or
polyether are used.
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Figure 4 : Computer reconstruction of
bitemark, 2003. Click the link below to find out more about this real life
case!
Picture adapted from : |
5. First aid
Attend to the victim immediately after that to
prevent infections. Human bites have higher risk of infections compared to
animal bites.
FORENSIC PHYSICAL COMPARISON OF EXHIBITS
At the moment, the computer is the most accurate tool to produce
transparent overlays. The comparisons of the exhibits can be performed by comparing photographs of the bitemarks using transparent overlays. Moreover, you can also directly compare the actual bitemark with the suspect's bitemark through test bites. Radiographic imaging and scanning electron microscopy are
also other methods which are reliable in helping to compare the suspect’s teeth
with the actual bitemark.
FORENSIC BIOLOGICAL EVIDENCE
The saliva samples collected by the forensic dentist is very useful in finding out the DNA profile of the depositor of the saliva. The beneficial thing about saliva is it has sufficient quantity and quality to allow PCR-based typing of the DNA that is exists in saliva from white blood cells (leucocytes) and also shedded epithelial cells.
What is PCR?
"The polymerase chain reaction (PCR) is a biochemical technology in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence."
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Figure 5 : PCR
Picture adapted from : |
CONCLUSION
In a nutshell, a simple bitemark is something that cannot be taken
lightly and is crucial because it helps in the investigation of the case. Don’t
you also think it is fascinating to know that a forensic dentist or forensic
odontologist is able to contribute so much in solving a crime? With the rapid
advancement of technology, our future forensic dentists will be able to uncover
more evidences and analyze findings more accurately. You must also take note
that a dentist should also be able to recognize bitemarks easily during regular
dental visits and be familiarized with it. With that, you can report the injury
to specific authorities if you suspect something is amiss.
Nevertheless, it is significant to acknowledge
the fact that forensic dentists play an important role in helping to solve the
crime by working hand in hand with other forensic scientists.
If you are interested in this field, you may conduct more research
about it.
The following below are references or links you may visit if you are
in thirst for more knowledge!
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