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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

Types of crime and crime scenes

Types of evidence

Biological evidence and DNA Profiles

Crime scene preservation

Chain of custody

Workshop topics:

Crimes and crime scenes

Murder

Burglary

Rape

Hijacking

What types of crimes occur in South Africa?

Crimes and crime scenes

Building Car Parking lot Body Home Office

What is a crime scene?

A crime scene is a place or body containing clues about who committed the crime.

Crimes and crime scenes

Locard’s Principle:

“every contact leaves a trace”

Crime scene

CriminalVictim

Crime scenes: Types of evidence

Crime scenes: Types of evidenceBLOOD 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

BOTTLE

CLOTHING

SEMEN

CIGARETTE BUTT

HAIR

Saliva

Blood

Skin cells

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

Identify or exclude a known suspect Link a suspect, witness or victim and crime

scene Identify missing persons

Because the DNA of all people is different we can:

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?

11, 23, 148, 2422, 1021, 1416, 711, 122, 323, 8X Y

A DNA profile is simply a unique list of numbers obtained from a person’s DNA.

The FSL does this by examining 10 regions (loci) in a person’s DNA.

LOCUS

9 markers will consist of a pair of numbers.

The 10th marker will specify sex.

MARKER

10 markers are required to build a DNA profile in SA.

22 X 22 Y

sperm

Inheritance of chromosomes

Each nucleus within a cell contains 46 chromosomes (23 pairs) in total

22 X 22 X

eggs

We inherit half from each parent

Father

22 pairsXY

22 pairsXX

Mother

DNA profiling: How it works

5%

95%

Functional DNANon-functional ("Junk" DNA)

4 different building blocks (A, C, G and T)

Non-functional DNA:• High proportion of sequence variation• Enough differences to make DNA unique

DNA profiling: How it works

ATCT ATCT ATCT ATCT ATCT ATCT ATCT

ATCT ATCT ATCT ATCT ATCT

Chr 11

Chr 11

Extract DNA out of sample and amplify DNA segments (PCR)

Separate and visualize DNA fragments using electrophoresis

Region (locus) on Chromosome 11 with repeated segments – short tandem repeats (STR)

Store profile as Numbers 5/7

Suspect 1

Suspect 2

Evidence

Uses of DNA Profiling: Matching evidence to suspectsMarker 1 Marker 2 Marker 3

Crime Scene

DNA profiles collected from evidence at the crime scene

11, 72, 323, 87, 113, 178, 1411, 142, 323, 22X Y

Evidence - Saliva Evidence - Blood

10, 195, 1823, 717, 1113, 1722, 239, 248, 221, 11X X

BLOODCIGARETTE BUTT

Crime scene evidence

No match

Suspect innocent

Confirms suspect was at the crime scene

✔Match (Hit)

Matching evidence to suspects

Suspect

South Africa’s National DNA Database

DNA profiles collected from crime scenes.

DNA profiles from certain suspects arrested for criminal offences.

DNA profiles are kept on a National DNA Database

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

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

Crime scene evidence National DNA Database

✔

Person previously arrested or convicted

Match

✔Match

Same criminal at many crime scenes

Matching evidence to DNA database

What else can we learn from a DNA profile?

A DNA profile, like a fingerprint, reveals no personal information and is merely a unique identifier.

DNA Profile

6, 917, 421, 193, 725, 11...

Fingerprint

haircolour?

eye colour?

height?

weight?

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.

C • Comfort and support victims

S • Secure the crime scene

I • Insist no one interferes

Crime scene preservation

D • Don’t touch

N • Note, record, observe

A • Assist police officers

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.

D - Don’t touch

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.

N - Note, record, observe

Provide assistance by requesting witnesses to wait near

the crime scene for an Investigating Officer.

Prevent non-essential people from entering the crime

scene.

A - Assist police officers

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.

C - Comfort and support victims

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.

S - Secure the crime scene

Crime scene management - SAPS

Crime scene manager Crime scene expert Crime scene investigator

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.

I - Insist no one interferes

Crime committed

Chain of custody

Evidence collected by CSI

Crime scene secured by first responding officer

DNA analysed at FSL

Suspect linked to crime scene

Suspect 1: 14,15 17,18 23,24Suspect 2: 15,18 17,19 23.2,24Evidence: 15,18 17,19 23.2,24

DNA profiles compared

WEAKEST LINK IN THE CHAIN

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