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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 Locards Principle: every contact leaves a trace Crime scene CriminalVictim
Crime scenes: Types of evidence
BLOOD WEAPONS FINGERPRINTS CIGARETTE BUTTBOTTLE CLOTHING SHOE PRINTS SEMEN
Types of evidence: Fingerprints Fingerprints can be used to uniquely identify a person
What is DNA? DNA contains the information that determines what we look like – its our blueprint Everyones 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
What is a DNA profile? 11, 2 3, 14 8, 24 22, 10 21, 14 16, 7 11, 12 2, 3 23, 8 X Y A DNA profile is simply a unique list of numbers obtained from a persons DNA. The FSL does this by examining 10 regions (loci) in a persons 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 X22 Y sperm Inheritance of chromosomes Each nucleus within a cell contains 46 chromosomes (23 pairs) in total 22 X eggs We inherit half from each parent Father 22 pairs XY 22 pairs XX Mother
DNA profiling: How it works 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 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 Store profile as Numbers 5/7
Suspect 1 Suspect 2 Evidence Uses of DNA Profiling: Matching evidence to suspects Marker 1Marker 2Marker 3
DNA profiles collected from evidence at the crime scene 11, 7 2, 3 23, 8 7, 11 3, 17 8, 14 11, 14 2, 3 23, 22 X Y Evidence - Saliva Evidence - Blood 10, 19 5, 18 23, 7 17, 11 13, 17 22, 23 9, 24 8, 2 21, 11 X BLOOD CIGARETTE BUTT
Crime scene evidence No match Suspect innocent Confirms suspect was at the crime scene Match (Hit) Matching evidence to suspects Suspect
South Africas National DNA Database DNA profiles collected from crime scenes. DNA profiles from certain suspectsarrested 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 evidenceNational 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, 9 17, 4 21, 19 3, 7 25, Fingerprint hair colour? 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 Dont 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 - Dont 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 managerCrime scene expertCrime 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 CSIs 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 1:14,1517,18 23,24 Suspect 2:15,1817, ,24 Evidence:15,1817, ,24 DNA profiles compared WEAKEST LINK IN THE CHAIN
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