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Brief History of Forensic DNA Typing
4/16/2017 Brief History of Forensic DNA Typing Ray White describes first polymorphic RFLP marker Alec Jeffreys discovers multilocus VNTR probes first paper on PCR FBI starts DNA casework first STR paper FSS starts UK DNA database FBI launches CODIS database
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What does DNA mean? Where can DNA be found?
DNA Typing 4/16/2017 What does DNA mean? Deoxyribonucleic Acid Where can DNA be found? Cell Cell Types - Blood - Muscle - Bone Marrow - Tooth Pulp - Hair Roots - Saliva - Sweat - Semen - Tissue Items - Chewing Gum - Stamps & Envelopes - Stains - Washed Stains - Door Knobs - Tooth brushes - Hair Brushes - Sanitary Pads Nucleus
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Individual nucleotides
DNA Typing 4/16/2017 DNA in the cell chromosome cell nucleus Double stranded DNA molecule Individual nucleotides Target Region for PCR
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DNA Inheritance Patterns are used in:
DNA Typing 4/16/2017 DNA Inheritance Patterns are used in: criminal paternity abandoned baby missing persons unidentified bodies
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Sources of biological evidence
DNA Typing 4/16/2017 Sources of biological evidence Blood Semen Saliva Urine Hair Teeth Bone Tissue
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DNA Use in Forensic Cases
DNA Typing 4/16/2017 DNA Use in Forensic Cases Most are rape cases (>2 out of 3) Looking for match between evidence and suspect Must compare victim’s DNA profile Challenges Mixtures must be resolved DNA is often degraded Inhibitors to PCR are often present
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On the victim (female) Vaginal swabs External genitalia swabs
DNA Typing 4/16/2017 On the victim (female) Vaginal swabs External genitalia swabs Rectal swabs Lick/kiss/bite areas Fingernail swabs Wood’s lamp positive areas
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On the victim (male) Penile swabs Rectal swabs Lick/kiss/bite areas
DNA Typing 4/16/2017 On the victim (male) Penile swabs Rectal swabs Lick/kiss/bite areas Fingernail swabs Wood’s lamp positive areas
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60% of kits are negative for semen
DNA Typing 4/16/2017 60% of kits are negative for semen Absence of sperm does not counter indicate sexual assault Reasons: vasectomy perpetrator failing to ejaculate 34% of rapist show evidence of sexual dysfunction at the time of rape time between exam and incident false report
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Steps in DNA Processing
DNA Typing 4/16/2017 Steps in DNA Processing Sample Obtained from Crime Scene or Paternity Investigation Biology DNA Extraction Quantitation PCR Amplification of Multiple STR markers Technology Separation and Detection of PCR Products (STR Alleles) Sample Genotype Determination Genetics Comparison of Sample Genotype to Other Sample Results If match occurs, comparison of DNA profile to population databases Generation of Case Report with Probability of Random Match
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Methods used for analysis of DNA
DNA Typing 4/16/2017 Methods used for analysis of DNA PCR (Polymerase Chain Reaction) - Sequence Variation and Tandem Repeat Variation - Small sample required - Used in CODIS
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TGCAT TGCAT TGCAT TGCAT TGCAT =5 Repeats
DNA Typing 4/16/2017 Repeat Variation TGCAT TGCAT TGCAT TGCAT TGCAT =5 Repeats TGCAT TGCAT TGCAT TGCAT = 4 Repeats MAY CONSISTS OF 2-7 NUCLEOTIDE REPEATS MOST STR’s HAVE 7-10 ALLELES PER LOCUS OFTEN WITH 2 OR 3 ALLELES THAT ARE COMMON
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4 6 7 DNA Profile =5,7 STR Short Tandem Repeat DNA Profile =4,6 5 AGAT
DNA Typing 4/16/2017 STR Short Tandem Repeat AGAT AGAT AGAT AGAT 6 4 AGAT AGAT DNA Profile =4,6 TCTA TCTA TCTA TCTA TCTA 7 5 TCTA TCTA DNA Profile =5,7
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PCR Four Main Steps 1) Isolation 2) Amplification - 3 steps
DNA Typing 4/16/2017 PCR Four Main Steps 1) Isolation 2) Amplification - 3 steps a) Denaturation b) Annealing Cycle c) Extension 3) Analysis / Interpretation 4) Statistics
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Isolation of DNA Blood Hair Roots Saliva Sweat Tissue DNA Chemical
DNA Typing 4/16/2017 Isolation of DNA Chemical DNA Blood Hair Roots Saliva Sweat Tissue
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Differential Isolation of DNA
DNA Typing 4/16/2017 Differential Isolation of DNA Semen stain Epithelial DNA Sperm DNA Chemical Semen stain Different Chemical Remove Epithelial DNA Sperm DNA
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Amplification (making copies) Solution Salt Primers Taq Bases DNA
DNA Typing 4/16/2017 Amplification (making copies) DNA Solution Salt Primers Taq Bases
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Amplification - The Cycles
DNA Typing 4/16/2017 Amplification - The Cycles 1 Cycle 2 Cycles 3 Cycles 4 Cycles 30 Cycles 5 Cycles
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Amplification - Denaturation
DNA Typing 4/16/2017 Amplification - Denaturation Step One T G C A G T C A T C A G Heat =
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Amplification - Annealing
DNA Typing 4/16/2017 Amplification - Annealing Step Two Flourescent or Color Tag Primer A G G C A T T C A G
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Amplification - Extension
DNA Typing 4/16/2017 Amplification - Extension Step Three Tag G T G A Primer C T A T T G A G T A G G C A T G A G T C A G C T C C G T A Taq Polymerase
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DNA Amplification with the Polymerase Chain Reaction (PCR)
DNA Typing 4/16/2017 DNA Amplification with the Polymerase Chain Reaction (PCR) Separate strands (denature) 5’ 3’ Starting DNA Template 5’ 3’ Add primers (anneal) 5’ 3’ Forward primer Reverse primer 5’ 3’ Make copies (extend primers)
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PCR Copies DNA Exponentially through Multiple Thermal Cycles
DNA Typing 4/16/2017 PCR Copies DNA Exponentially through Multiple Thermal Cycles Original DNA target region Thermal cycle Thermal cycle Thermal cycle In 32 cycles at 100% efficiency, 1.07 billion copies of targeted DNA region are created
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Short Tandem Repeats (STRs)
AATG 7 repeats 8 repeats the repeat region is variable between samples while the flanking regions where PCR primers bind are constant Homozygote = both alleles are the same length Heterozygote = alleles differ and can be resolved from one another
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ABI Prism 310 Genetic Analyzer
DNA Typing 4/16/2017 ABI Prism 310 Genetic Analyzer capillary Syringe with polymer solution Autosampler tray Outlet buffer Injection electrode Inlet buffer
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Close-up of ABI Prism 310 Sample Loading Area
DNA Typing 4/16/2017 Close-up of ABI Prism 310 Sample Loading Area Autosampler Tray Sample Vials Electrode Capillary See Technology section for more information on CE
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DNA Typing 4/16/2017
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Human Identity Testing with Multiplex STRs
DNA Typing 4/16/2017 Human Identity Testing with Multiplex STRs Simultaneous Analysis of 10 STRs and Gender ID AmpFlSTR® SGM Plus™ kit Two different individuals DNA Size (base pairs) amelogenin D19 D3 D8 TH01 VWA D21 FGA D16 D18 D2 Results obtained in less than 5 hours with a spot of blood the size of a pinhead probability of a random match: ~1 in 3 trillion
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DNA Typing 4/16/2017 STR genotyping is performed by comparison of sample data to allelic ladders Microvariant allele
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DNA Typing 4/16/2017
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Multiplex PCR Over 10 Markers Can Be Copied at Once
DNA Typing 4/16/2017 Multiplex PCR Over 10 Markers Can Be Copied at Once Sensitivities to levels less than 1 ng of DNA Ability to Handle Mixtures and Degraded Samples Different Fluorescent Dyes Used to Distinguish STR Alleles with Overlapping Size Ranges
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An Example Forensic STR Multiplex Kit
DNA Typing 4/16/2017 An Example Forensic STR Multiplex Kit AmpFlSTR® Profiler Plus™ Kit available from PE Biosystems (Foster City, CA) 9 STRs amplified along with sex-typing marker amelogenin in a single PCR reaction 100 bp 400 bp 300 bp 200 bp Size Separation Color Separation D3 FGA vWA 5-FAM (blue) D13 D5 D7 NED (yellow) A D8 D21 D18 JOE (green) GS500-internal lane standard ROX (red)
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DNA Typing 4/16/2017
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DNA Typing 4/16/2017
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Freq of the match is about 1 in 520,000,000,000 in the Cauc pop
DNA Typing 4/16/2017 STR Results The DNA from the evidence stain and the reference sample from the suspect match. Freq of the match is about 1 in 520,000,000,000 in the Cauc pop 1 in 618,500,000,000 in the AA pop 1 in 532,000,000,000 in the Hispanic pop.
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13 CODIS Core STR Loci with Chromosomal Positions
DNA Typing 4/16/2017 13 CODIS Core STR Loci with Chromosomal Positions TPOX D3S1358 TH01 D8S1179 D5S818 VWA FGA D7S820 CSF1PO AMEL D13S317 AMEL D16S539 D18S51 D21S11
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Pet DNA Snowball the cat owned by suspect LA Times March 16, 2002
DNA Typing 4/16/2017 Pet DNA Snowball the cat owned by suspect White cat hairs found on victim’s body Matched cat hairs to those found on victim’s body Meowplex for cats LA Times March 16, 2002 Ventura County woman sexually assaulted in her home Victim described suspect Police canvassed neighborhood found individual matching suspect Dog hair recovered from his pants matching victim’s dog
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Human Identity Testing
DNA Typing 4/16/2017 Human Identity Testing Forensic cases -- matching suspect with evidence Paternity testing -- identifying father Historical investigations Possible offspring of Thomas Jefferson and Sally Hemmings Missing persons investigations Mass disasters -- putting pieces back together Tsunami survivors Infants returned to parents using DNA
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Human Identity Testing
DNA Typing 4/16/2017 Human Identity Testing Military DNA “dog tag” 4 sets of remains from WWI, WWII, Korea and Vietnam All matched to family members Future no more unknown soilders Each soldier has a blood card stored in freezer 4.5 million samples Convicted felon DNA databases Innocence project As of 3/8/07, 196 prisoners have been released Thousands have come back as a match
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FBI’s CODIS DNA Database
DNA Typing 4/16/2017 FBI’s CODIS DNA Database Combined DNA Index System Used for linking serial crimes and unsolved cases with repeat offenders Launched October 1998 Links all 50 states Requires >4 RFLP markers and/or 13 core STR markers Current backlog of >600,000 samples
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(Combined DNA Indexing System)
DNA Typing 4/16/2017 CODIS (Combined DNA Indexing System) 1) Law requiring collection of convicted offender samples 2) Databasing of the DNA profile from offenders 3) DNA Typing of evidentiary samples a) Unknown suspect cases 4) Search a national database a) Compare samples to the database b) Compare cases to each other
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Weekly searches at each level
DNA Typing 4/16/2017 CODIS Over 1 million profiles at national level Local Database State Database National Database Weekly searches at each level
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CODIS Population Index Casework Index Convicted Offender Index
DNA Typing 4/16/2017 CODIS Population Index Casework Index Convicted Offender Index
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HITS Case to case--links 2 or more cases
DNA Typing 4/16/2017 HITS Case to case--links 2 or more cases aids investigation, one of the cases may be a solved case Case to offender links case to convicted offender
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WHY THE CHANGE? New Data Database Successes
DNA Typing 4/16/2017 WHY THE CHANGE? Database Successes Virginia is averaging one “cold hit” per week in 2001. Diversion of resources to other cases. New Data Approximately 85% of hits would have been missed if the databank were limited to only violent offenders 52% of Florida offenders linked to sexual assaults and homicides by DNA database matches have had prior burglary convictions.
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WHY THE CHANGE? Citizen Demand / Pubic Safety
DNA Typing 4/16/2017 WHY THE CHANGE? Citizen Demand / Pubic Safety Consider the following US Department of Justice statistics: The average rapist commits 8-12 sexual assaults. Of 108,580 persons released from prisons in 11 States in 1983, an estimated 62.5% were rearrested for a felony or serious misdemeanor within 3 years 46.8% were reconvicted, and 41.4% returned to prison or jail.
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DNA DATABASE SUCCESSES
DNA Typing 4/16/2017 DNA DATABASE SUCCESSES Virginia Database Statistics Over 1100 DNA database hits 85% of hits would have been missed if database limited to only violent offenders. Florida Database Statistics 52% of Florida offenders linked to sexual assaults and homicides by DNA database matches have had prior burglary convictions. New York Database Statistics 1999 New York law expands DNA database to include many non-violent felonies (including burglary and drug crimes). January 2002 Report “The First 100 Hits.” February 2000 – July 2001 104 crime scenes matched with 102 offenders.
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