Transcript Slide 1

Welcome
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DNA Awareness Workshop
DNA Awareness Workshop
DNA Awareness Workshop
Aims of the workshop:
 To provide an explanation of how DNA/
biological evidence can help to solve crimes.
 The important role we play as a first responder
in ensuring that a crime scene is properly
secured and protected.
DNA Awareness Workshop
Workshop topics:
 Types of crime and crime scenes
 Types of evidence
 Biological evidence and DNA Profiles
 Crime scene preservation
 Chain of custody
Crimes and crime scenes
What types of crimes occur in South Africa?
 Murder
 Burglary
 Rape
 Hijacking
Crimes and crime scenes
What is a crime scene?
A crime scene is a place or body containing clues
about who committed the crime.
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Building
Car
Parking lot
Body
Home
Office
Crimes and crime scenes
Locard’s Principle:
“every contact leaves a trace”
Crime scene
Victim
Criminal
Crime scenes: Types of evidence
Crime scenes: Types of evidence
BLOOD
WEAPONS
FINGERPRINTS
CIGARETTE BUTT
BOTTLE
CLOTHING
SHOE PRINTS
SEMEN
Types of evidence: Fingerprints
Fingerprints can be used to uniquely identify a person
Types of evidence: Sources of DNA
Types of evidence: Biological (DNA)
BLOOD
HAIR
Saliva
Blood
CIGARETTE BUTT
CLOTHING
Skin cells
Semen
BOTTLE
SEMEN
Hair
Sweat
DNA – deoxyribonucleic acid
Biology 101
What is DNA?
DNA contains the information
that determines what we look like
– it’s our “blueprint”
Everyone’s DNA is different
(except for identical twins)
What is DNA?
DNA is found in all cells in our bodies
(except red blood cells)
The DNA in every cell of our bodies is identical
DNA in forensic investigations
Because the DNA of all people is different we can:
 Identify or exclude a known suspect
 Link a suspect, witness or victim and crime
scene
 Identify missing persons
Contamination of DNA evidence
 DNA evidence can easily become contaminated.
 Contamination can occur when DNA from another
source is mixed with the DNA evidence.
 Heat, sunlight, moisture, bacteria and even mould may
damage or affect the quality of the DNA evidence
collected at a crime scene thereby rendering it useless
to the police.
Evidence collection kits
Buccal swab
DNA Profiles
What is a DNA profile?
MARKER
11, 2
LOCUS 3, 14
8, 24
22, 10
21, 14
16, 7
11, 12
2, 3
23, 8
XY
A DNA profile is simply a unique list
of numbers obtained from a
person’s DNA.
10 markers are required to build a
DNA profile in SA.
The FSL does this by examining 10
regions (loci) in a person’s DNA.
9 markers will consist of a pair of
numbers.
The 10th marker will specify sex.
Inheritance of chromosomes
Each nucleus within a cell contains 46 chromosomes
(23 pairs) in total
We inherit half from each parent
Mother
Father
22 pairs
XX
22 pairs
XY
eggs
sperm
22 X
22 X
22 X
22 Y
DNA profiling: How it works
4 different building blocks (A, C, G and T)
Functional DNA
Non-functional ("Junk" DNA)
5%
95%
Non-functional DNA:
• High proportion of sequence variation
• Enough differences to make DNA unique
DNA profiling: How it works
Region (locus) on Chromosome 11 with repeated segments – short tandem repeats (STR)
Chr 11
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
ATCT
Chr 11
Extract DNA out of sample and amplify DNA segments (PCR)
Separate and visualize DNA fragments using electrophoresis
Store
profile
as
Numbers
5/7
ATCT
Uses of DNA Profiling: Matching evidence to suspects
Marker 1
Suspect 1
Suspect 2
Evidence
Marker 2
Marker 3
Crime Scene
DNA profiles collected from evidence at the crime scene
Evidence - Saliva
11, 7
2, 3
23, 8
7, 11
3, 17
CIGARETTE BUTT
8, 14
11, 14
2, 3
23, 22
XY
Evidence - Blood
10, 19
5, 18
23, 7
17, 11
13, 17
BLOOD
22, 23
9, 24
8, 2
21, 11
XX
Matching evidence to suspects
Suspect
Crime scene
evidence
✔
No match
Suspect
innocent
Match (Hit)
Confirms suspect was
at the crime scene
South Africa’s National DNA Database
DNA profiles are kept on a National DNA Database
 DNA profiles collected from crime scenes.
 DNA profiles from certain suspects arrested for
criminal offences.
Legislation regulating the use of DNA evidence
 Currently no specific legislation exists in SA.
 Section 37 of the Criminal Procedure Act, 51 of
1977 is the only statutory provision that deals with
ascertainment of bodily features of an accused.
 The Criminal Law (Forensic Procedures)
Amendment Bill B9B-2013 (“DNA Bill”) has been
drafted to address the lack of legislation.
The ‘DNA Bill’
 Crime Scene Index: DNA profiles obtained from biological
evidence collected from crime scenes
 Arrestee Index: DNA profiles taken from persons arrested for,
or suspected of having committed, a Schedule 8 offence
 Convicted Offender Index: DNA profiles of convicted
offenders (Schedule 8 offences)
The ‘DNA Bill’
 Investigative Index: DNA profiles from persons taken with
informed consent or by warrant, if necessary, for the purpose
of investigating an offence
 Elimination Index: DNA profiles of people working in the
collection and analysis of forensic samples
 Missing persons & unidentified human remains Index: DNA
profiles of missing persons and unidentified human remains
Schedule 8 Offences
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Murder
Culpable homicide
Rape or compelled rape
Sexual assault, compelled sexual assault or compelled
self-sexual assault
Any sexual assault against a child or person who is
mentally disabled
Trafficking in persons for sexual purposes
Robbery
Kidnapping
Arson
Matching evidence to DNA database
Crime scene evidence
National DNA Database
Match
Match
✔
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Person previously
arrested or convicted
Same criminal at
many crime scenes
What else can we learn from a DNA profile?
Fingerprint
DNA Profile
hair
colour?
eye colour?
height?
6, 9
17, 4
21, 19
3, 7
25, 11
...
weight?
A DNA profile, like a fingerprint, reveals no personal
information and is merely a unique identifier.
How to be prepared when arriving at a crime scene
 Good planning, organisation and co-ordination will
ensure valuable forensic evidence will be preserved.
 Arriving unprepared may result in missed
opportunities.
 Bad organisation can result in evidence being lost.
 Having too many unqualified people involved at a
crime scene runs the risk of contaminating or
destroying important evidence.
Crime scene preservation
D • Don’t touch
N • Note, record, observe
A • Assist police officers
C • Comfort and support victims
S • Secure the crime scene
I • Insist no one interferes
D - Don’t touch
 Nothing should be touched unless absolutely necessary.
 Wear protective clothing if you absolutely have to enter
the crime scene.
 Use a single path when entering and leaving.
 Do not use any facilities at the scene and avoid eating,
drinking or smoking at the scene.
 Avoid moving anything or anybody from the original
location.
N - Note, record, observe
 Make notes with sketches and if need be take photos,
video and/or measurements.
 Note time of arrival.
 Identify and note signs of any activities.
 Note who is present, is seen leaving or has entered the
scene.
A - Assist police officers
 Provide assistance by requesting witnesses to wait near
the crime scene for an Investigating Officer.
 Prevent non-essential people from entering the crime
scene.
C - Comfort and support victims
 Offer comfort and aid at the crime scene without
disturbing the crime scene.
 Consider health and safety risks such as body fluids and
broken glass.
 Note: If there is a conflict between preservation of
evidence and saving a life, priority is always given to
emergency medical care.
S - Secure the crime scene
 Demarcate a larger area first than a smaller one.
 Use a physical barrier to cordon off the scene.
 Prevent non-essential people from entering.
 Make a note if any non-essential people were in the
cordoned off area before the barrier was erected.
Crime scene management - SAPS
Crime scene manager
Crime scene expert
Crime scene investigator
I - Insist no one interferes
 The crime scene may contain valuable evidence and
the less people who enter the scene, the greater the
chance of finding uncontaminated DNA evidence.
 Access should ideally be limited to the CSI’s and
medical personnel who are attending to the victims
present at the scene.
Chain of custody
WEAKEST LINK IN THE CHAIN
Crime committed
Suspect linked to crime scene
Suspect 1:
Suspect 2:
Evidence:
14,15
15,18
15,18
17,18
17,19
17,19
Crime scene secured by first
responding officer
23,24
23.2,24
23.2,24
DNA profiles compared
Evidence collected by CSI
DNA analysed at FSL
Thank you
Please visit our website
www.dnaproject.co.za
or follow us on
Facebook and
Twitter