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1. Forensic Chemistry lecture
Week 10
CONCEPT 0f DNA
HAIRS

2. Concept of DNA
DEOXYRIBONUCLEIC ACID (DNA)
DNA Overview - All organisms are made up of cells.
The average human has approximately 100
trillion cells. All cells except red blood cells
contain genetic material known as
Deoxyribonucleic Acid (DNA).
Deoxyribonucleic acid (DNA) is a nucleic acid that
contains the genetic instructions used in the
development and functioning of all known living
organisms with the exception of some viruses.

3. The main role of DNA molecules is the long-term
storage of information. DNA is often compared to
a set of blueprints, like a recipe or a code, since it
contains the instructions needed to construct
other components of cells, such as proteins and
RNA molecules. The DNA segments that carry this
genetic information are called genes, but other
DNA sequences have structural purposes, or are
involved in regulating the use of this genetic
information.
DNA is a powerful tool because each person's DNA
is different from every other individual's, except
for identical twins. Because of that difference,
DNA collected from a crime scene can either link

4. a suspect to the evidence or eliminate a suspect,
similar to the use of fingerprints. It also can
identify a victim through DNA from relatives,
even when nobody can be found. And when
evidence from one crime scene is compared with
evidence from another, those crime scenes can
be linked to the same perpetrator.
a. Where Is DNA Contained in the Human Body?
DNA is contained in blood, semen, skin cells,
tissue, organs, muscle, brain cells, bone, teeth,
hair, saliva, mucus, perspiration, fingernails,
urine, feces, etc.

5. b. Physical vs Biological Evidence
Physical evidence is any tangible object that can
connect an offender to a crime scene. Biological
evidence, which contains DNA, is a type of
physical evidence. However, biological evidence is
not always visible to the naked eye.
c. DNA Testing
DNA testing has expanded the types of useful
biological evidence. All biological evidence found
at crime scenes can be subjected to DNA testing.
Samples such as feces and vomit can be tested,
but may not be routinely accepted by
laboratories for testing.

6. d. DNA Analysis
DNA analysis is similar to fingerprint analysis in
how matches are determined. Evidence collected
from a crime scene is compared to a known
sample. If each feature is not identical, the DNA
evidence is determined NOT to be a match and
therefore did NOT come from the suspect.
e. Where can DNA evidence be found at a crime
scene?
DNA evidence can be collected from virtually
anywhere. DNA has helped solve many cases
when imaginative investigators collected
evidence from non traditional sources. One
murder was solved when the suspect's DNA,

7. taken from saliva in a dental impression mould,
matched the DNA swabbed from a bite mark on
the victim. A masked rapist was convicted of
forced oral copulation when his victim's DNA
matched DNA swabbed from the suspect's penis
6 hours after the offense. Numerous cases have
been solved by DNA analysis of saliva on cigarette
butts, postage stamps, and the area around the
mouth opening on skin masks. DNA analysis of a
single hair (without the root) found deep in the
victim's throat provided a critical piece of
evidence used in a capital murder conviction.

8. IMPORTANCE OF DNA EVIDENCE IN CRIME
INVESTIGATION
"DNA evidence “– constitutes the totality of the DNA
profiles, results and other genetic information directly
generated from DNA testing of biological samples.
a. DNA in Criminal Investigations
1. The same DNA is found in all cells of the body.
2. The same DNA profile is recovered, no matter what
the sample (cell) type.
3. Your DNA does not change through your life.
4. Any cellular material left at a crime scene may be a
useful source of DNA helix.

9. b. Applications of DNA Analysis
1. Criminal Investigations - matching suspect
with evidence.
2. Parentage Testing - identifying parent(s)
3. Historical investigations
4. Missing persons’ investigations
5. Mass disasters - positive identification of
the deceased
6. Military DNA “dog tag”
7. Convicted felon DNA databases

10. c. Some Examples of DNA Uses for Forensic
Identification
1. Identify potential suspects whose DNA may
match evidence left at crime scenes.
2. Exonerate persons wrongly accused of crimes.
3. Identify crime and catastrophe victims.
4. Establish paternity and other family relationships.
5. Identify endangered and protected species as an
aid to wildlife officials (could be used for
prosecuting poachers)
6. Detect bacteria and other organisms that may
pollute air, water, soil, and food.

11. 7. Match organ donors with recipients in transplant
programs.
8. Determine pedigree for seed or livestock breeds.
9. Authenticate consumables such as caviar and wine.
2. SEARCH FOR DNA EVIDENCE
Items of physical evidence are not always visible to
the naked eye and may be easily overlooked. A
methodical approach to collection and preservation of
evidence is essential. One exception may be if evidence
integrity is at risk. Under those circumstances, it is
important that rapid decisions be made to prevent
degradation or loss of evidence.

12. An alternate light source or oblique lighting may be used
to identify some types of biological evidence. A sample
detected with the ALS should be properly collected and
packaged with a label noting that it is a biological
sample.
Based on these considerations, this method can be a
valuable tool. It is generally used only after exhausting
other options.
3. DNA Evidence is Trace Evidence
Trace evidence, such as hair, fibers and body fluids,
are types of physical evidence that is small & transient,
but measurable. When larger items of physical
evidence are subjected to closer examination in the
laboratory, trace evidence may be detected.

13. The importance of trace evidence can be critical to
an investigation. Awareness of this type of
evidence cannot be overemphasized.
Photographing the area where any evidence is
collected not only provides documentation of the
collection but also assists in locating trace
evidence.
Even if identification cannot be made in the
laboratory, the investigator and prosecutor may
use trace evidence as part of a convincing
circumstantial case. Skill and effort during
collection, testing and case preparation can help
ensure a successful presentation of trace
evidence in the courtroom.

14. b. DNA Evidence is Transfer Evidence
When DNA evidence is transferred by direct or
secondary (indirect) means, it remains on
surfaces by absorption or adherence. In general,
liquid biological evidence is absorbed into
surfaces, and solid biological evidence adheres to
surfaces.
c. Evidence Search Methods
The scene and conditions may determine the
search method to use. For example, the size of
the crime scene and the number of people
available to conduct the search may play a role in
determining the best method to use.

15. 3. COLLECTION OF DNA EVIDENCE
Collection and packaging methods differ
depending on the type of evidence and the
material upon which it is found. It is
preferable to collect evidence in its original
state. If the evidence is fragile or can easily be
lost, the entire object should be collected and
packaged when size and circumstances
permit. Contact a specialist if you are not
trained in the required procedure.

16. a. Collection Priority
Prioritize the order in which evidence will be
collected at the scene. Collect biological
evidence, trace materials and evidence of a
fragile nature is first. The second priority would
be to collect swabs from handled items that have
been moved, are out of place or do not belong to
the resident. A third priority type of evidence
that may be at the scene includes the potentially
lower-quality biological evidence.
Circumstances & local agency procedures may
dictate priority process. Investigators should
contact their local laboratory for specific
collection procedures.

17. 1. First Priority
Items that potentially contain sufficient amounts of
DNA to obtain a profile are the most important
evidence and the first priority to collect.
However, the collection or swabbing of certain
items may depend on whether or not residents
are available to ask if these items are theirs, or if
residents had the opportunity to talk to the
responding investigator to indicate which items
do or do not belong to them. Examples of these
items are as follows:
a. Blood
b. Cigarette butts

18. c. Bottles, cans and drinking containers not used by the
residents (collect the item and submit it to the lab if no
liquid remains in the container or use one slightly
moistened swab to sample around the mouth opening).
d. Hairs found or caught in splintered wood or broken glass at
the point of entry.
e. Discarded latex gloves.
f. Clothing items, bandannas, masks or hats that do not
belong to the residents.
g. Sunglasses or eyeglasses left behind by the suspect
(collect the glasses and submit them to the lab or use one
slightly moistened swab to sample the parts that rest on
the ear, the bridge of the nose, and the bottoms of the
frames that rest on the face underneath the eyes).
Toothpicks, chewed gum, sunflower seed hulls, lollipop
sticks

19. h. Cell phone left by the suspect (collect the item and
submit to the lab, or use one slightly moistened swab
to sample around the mouthpiece and a second slightly
moistened swab to sample around the earpiece).
i. Food items with bite marks — some food samples can
degrade quickly at room temperature; sample the area
around the bite mark with a slightly moistened swab at
the scene (collect the food item and store it frozen).
j. Evidence that might have semen on it (e.g., panties
removed from a bedroom drawer and found crumpled
up in another room).
Note: One alternate swabbing technique is to use a
slightly moistened swab for collection, followed by a
dry swab. Both swabs should be marked and may be
packaged together.

20. 2. Second Priority
The second priority would be to collect swabs from handled
items that have been moved, are out of place or do not
belong to the resident. Examples of these are as follows:
a. Pry bars.
b. Tools.
c. Jewelry boxes or watch cases not in their usual location,
with the contents missing or scattered (for jewelry boxes
that have been moved or the contents removed, use one
slightly moistened swab around the edges of the box that
would have been touched or held onto when opening it).
d. Cash boxes, cash register drawers.
e. Keys left behind by suspect.
f. Computer connectors or cables left behind if the monitor,
printer or the computer was stolen

21. When sampling this type of evidence, collect as
much sample as possible from a single source on
a single swab. If the swab becomes very dirty or
damaged in the process, use a second swab. If
residual moisture remains on an item after using
the first swab, use a second dry swab.
Concentrate the biological evidence from one
item on one swab, on the tip. Collect control
samples per agency guidelines.
3. Third Priority
A third priority type of evidence that may be at
the crime scene includes the following
a. Smudged fingerprints (unsuitable for
identification) near point of entry.

22. b. Door knobs on doors leading to the exterior.
c. Latches or handles of gates left open.
An example is the handles of tools. Use
one slightly moistened swab to sample the
handle of the tool. If an item has two ends
that could have been handled, such as a tire
iron or pry bar, use one swab for each end.
Keep the biological evidence collected from
one item on one swab, preferably on the tip.
Collect control samples per agency guidelines.

23. 4. HANDLING AND PRESERVATION OF DNA
EVIDENCE
a. Do’s and Don’t’s in Handling and Preservation
of Biological Evidence for DNA Analysis
DO’s
a. Ensure that proper chain of custody is
maintained in the handling of physical evidence
b. Recovered pieces of evidence from the crime
scene must be properly preserved and
documented. They must be properly identified
for purposes of court presentation.
c. Have separate containers for different samples.

24. d. Place blood or liquid tissues in spill-proof
containers.
e. Immediate extraction of DNA samples from
the biological evidence is a must.
f. Materials in contact with the samples should
be sterile.
g. When collecting any type of body fluid or
tissue always wear gloves and additional
protective device when appropriate.
h. Blood samples must be refrigerated.

25. DON’T’S
a. DNA test is very sensitive and vulnerable to
contamination by other DNA sources. Avoid
contamination with other human DNA.
b. Do not handle samples with bare hands.
c. Avoid long-term storage of tissues.
d. No ice is required and dry ice should never be
used to cool the tube of blood.
e. Do not mouth pipette anybody fluid
regardless of the source.

26. f. Avoid drying of wet stained garments under
directs sunlight or exposing it to an electric fan.
g. Do not collect a wet garment or garment with a
wet bloodstain in a sealed air-tight container.
h. Do not use plastic bag in the collection of blood
specimen.
b. Packaging for Transport
Use plastic bags for the transportation of
biological evidence only when there are excessive
body fluids and possible contamination of people
and other evidence items. Use paper packaging if
saturation is not a possibility.

27. Never package wet or moist body fluids in plastic bags for
long periods of time. This promotes bacterial growth
and evidence contamination, which can lead to DNA
degradation.
c. Transportation and Short-Term Storage
Before collecting any evidence at a crime scene, secure a
place for temporary storage. This will help to prevent
any degradation or contamination of biological
evidence.
Direct sunlight and warmer conditions may cause DNA to
degrade more rapidly. Avoid storing evidence in places
that may get hot, such as the trunk of a police car. To
best preserve biological evidence.

28. d. Preserving Evidence
From crime scene to forensic laboratory to courtroom, all
evidence must be identified, inventoried and secured
to preserve its integrity. It is important to demonstrate
that the evidence introduced at trial is the same
evidence collected at the crime scene and that access
was controlled and documented. An understanding of
and adherence to the rules governing chain of custody
is vital for an investigator to ensure evidence
admissibility in court.
Effective evidence preservation includes appropriate
packaging with correct and consistent information on
labelling and procedural documentation for all items.

29. Biological evidence should be air-dried before
packaging to minimize degradation. Packaging
in paper is preferred; however, some
laboratories allow packaging in plastic if the
sample is thoroughly dried.
Liquid samples, such as water from a toilet bowl
or pipes, should be properly documented and
packaged in sterile glass or plastic containers
and refrigerated as soon as possible to avoid
contamination of evidence that may contain
DNA, always take the following precautions:

30. a. Wear gloves. Change them often.
b. Use disposable instruments or clean them
thoroughly before and after handling each
sample.
c. Avoid touching the area where you believe DNA
may exist.
d. Avoid talking, sneezing, and coughing over
evidence.
e. Avoid touching your face, nose, and mouth when
collecting and packaging evidence.
f. Air-dry evidence thoroughly before packaging.
g. Put evidence into new paper bags or envelopes,
not into plastic bags. Do not use staples.

31. e. Personal protection:
Biological materials can contain pathogens
such as Hepatitis, Syphilis, TB, Gonorrhea,
Measles, HIV, etc.
NOTE: Assume that all stains, wet or dry, are
infectious
f. Problems with DNA Evidence
Degradation – is the breaking down of DNA into
smaller fragments by chemical or physical
processes.
Contamination – occurrence of having unwanted
DNA profile in the specimen.

32. g. Degradation
a. DNA can be degraded.
b. Affected by certain conditions.
c. Normally inside a body or a living cell, conditions are
perfectly maintained to avoid DNA degradation.
d. When it leaves the body, these conditions are
uncontrolled.
h . Factors Affecting DNA Degradation
a. Temperature – the higher the temperature, the faster the
degradation of DNA evidence proceeds.
b. pH – DNA can be degraded by alkalinity or acidity of the
matrix.
c. Humidity
d. Exposure to sunlight
e. Exposure to chemicals

33. i. Contamination
a. Addition of different person’s physiological
material after crime during collection, during
examination or anywhere in between.
b. Maybe accidental or purposely.
c. Invalidates DNA evidence completely.
j. Contamination vs Degradation
a. Degradation does not change the genotype of
the evidence while contamination does.
b. Contamination could produce false positive
result while degradation does not.
c. Both alter the TRUE result.
d. Both should be avoided.

34. k. Mixed Samples
a. Not the same as contamination.
b. Mixed sample contains more than 1 person’s DNA.
c. Happened before or during the crime.
Examples:
Semen and vaginal epithelial cells in rape cases.
Married couple sharing house.
l. Avoiding Contamination
a. Always wear clean gloves.
b. Change gloves between samples.
c. Use clean (sterilized) collection tools.
d. Proper labelling and packaging of evidence.

35. e. Slowing the degradation
f. Removing moisture.
g. Lowering temperature.
h. Avoid exposure to chemicals and direct sunlight.
1. If items have been stored properly, DNA can
last decades (30+ years).
2. Exposed to harsh environment (eg: heat,
sunlight, moisture, mould), DNA may only last a
few days or weeks.
3. In the laboratory: we can’t tell in advance
whether or not an item will yield any DNA.
DNA can be present, but too degraded to give a
result (partial DNA profile).

36. 6. Documentation and labelling
a. Documents Needed:
1. Letter Request – An ideal letter request contains
all information as to:
•
– Brief summary of the case
– Source of the specimen
– Markings of the specimen
– The way the evidence is packed.
•
2. Chain of Custody Form – May contained in the
packaging of the evidence.
•
3. Court Order – For cases already in court.
•

37. b. Chain of Custody – Record of individuals who
have had physical possession of the evidence.
• NOTE: Integrity of chain of custody
“The fewer people handling the evidence, the
lesser the chance of contamination and a
shorter chain of custody for court
admissibility.”
c. Seal – To maintain integrity of the specimen;
to further prove that no tampering took
placed.

38. d. Markings - These are information to ensure that the
items can be identified by the collector at any time in
the future. This precaution will help immeasurably to
establish the credibility of the collector’s report or
testimony and will effectively avoid any suggestions
that the item has been misidentified.
Markings on the specimen must at least contain
the following:
•
a. Exhibits and/or SOCO Case # (for SOCO
personnel)
b. Initials and/ or signature of the collecting officer.
c. Time and date of collection.
d. It is also important to note the place or location
where the evidence was collected.

39. Hairs
Hair is a filamentous outgrowth of dead cells
from the skin found only on mammals.
Purposes of examination:
• To determine whether the hair in questioned
originated from an animal or human being
and the comparison of questioned and known
hairs.

40. • To ascertain whether two or more individuals
could have come into contact or whether one or
more individuals could have come into contact
with an object.
The examination of this associative evidence is
useful in the crimes of violence, such as
homicide, sexual assault, and aggravated assault,
where physical contact may have occurred.
Crimes such as burglary and armed robbery
typically involve the recovery of debris and
articles of clothing which may contain hairs useful
for identification of suspects.

41. Hair is one of the most common type of trace
evidence found at the crime scene. Hair transfer
may occur during physical contact of the suspect
and the victim. Hair may fall out under condition
that suspect is unaware of & unable to guard
against it.
Value of Hair as Evidence
The value of hair as evidence in the criminal cases
has been clearly recognized. It is seldom
conclusive as evidence, but in conjunction with
other details, has proven to be an important and
essential aid to the investigator.

42. Facts about Hair
a. Each individual hair is formed inside a hair bulb
deep in a hair follicle.
b. The follicle is a tiny but powerful factory which
throughout many people’s lifetime continues to
produce hair.
c. The primary component of hair is keratin.
d. Keratins are proteins, long chains (polymers) of
amino acids.
e. The average human head has about 100,000
hair follicles. Some people have as many as
150,000.

43. f. Each follicle can grow about 20 individual hairs in
a person’s lifetime.
g. Each new hair grows for several years & can
reach over a meter in length.
h. Average hair loss is about 100 strands a day.
i. As anytime around 80-90% of most people’s hair
follicles are in the anagen or growing phase, 2%
are in the catagen phase or the transition period
between the anagen and the telogen phase or
resting phase which are about 10- 18%, where
hair are routinely lost.
j. Next to teeth and bones, it is also one of the
most decay-resistant human elements.

44. Hair Structure
3 Parts of Hair
Root bulb- the shape of the root bulb will
determine if the hair was pulled by force or not.
Porti Cuticle – is the outer surface of the hair and
when viewed under a microscope appears to be
composed of scale like flakes, each overlapping
the others like the scale of a fish.
Medulla or Core – is the central canal of the hair
shaft. It could be continuous, fragmented,
interrupted or absent and begins more or less
with the root.

45. • Cortex – the intermediate and the thickest
layer of the shaft and is composed of
elongated, spindle shaped fibrils which cohere
and contains the colour pigmentation of the
hair embedded in the skin
• Hair shaft – contains the most information
about the hair and portion above the surface
of the skin. It is the most distinctive part of
the hair.
• Tip – will show if the hair is cut, burned or if it
has split ends.