Margaret AcevesState of CaliforniaDept. Of Justice

Jan Bashinski DNA Laboratory

If Case goes to Court, Our role as Criminalists is to present the facts to the

jury

Case approach is to leave sufficient evidence for re-analysis.

DNA Criminalist in courtDeputy District Attorney qualifies DNA Analyst as

an expert through their education, training and experience

What is DNA is explained to the court and jury.The DNA Analysis is briefly explainedSpecific DNA results are presented Significances of match is explained

Education of a DNA Analyst A Bachelors degree in a Natural Science

AND

FBI requires specific courses to participate in CODIS Molecular Biology Genetics Biochemistry Training in statistics

Qualifying as an Expert

•Training of a DNA Analyst

•Experience of a DNA Analyst

•How many cases completed•How many times have you testified•Results of Proficiency

DNA BasicsWhat is DNA?

DNA stands for Deoxyribonucleic Acid

• It is the genetic material found in all plants and animals.• “Blueprint of Life” – It contains all of the information for

passing genetic traits from one generation to the next generation.

Where is DNA found in your body?

Our bodies are made up of cells.

The nucleus of each cell contains DNA.

Types of Biological EvidenceBloodBloodSemenSemenSalivaSalivaHairHairSweatSweatTeethTeethBoneBoneTissueTissueUrineUrine

Important Point: All cells in your body have the same DNA.

How is DNA inherited?

½ is inherited from your Mother½ is inherited from your Father

DNA is packaged in the form of chromosomes.

Humans have 23 pairs of chromosomes.

Terms to Understand

Chromosome – Physical structure that DNA is packaged in. Humans have 23 pairs.

Genetic Marker (locus) – specific location on a chromosome.

Allele – Alternative possibility for a genetic marker.

Forensic DNA TypingMore than 99% of our DNA is the same (this is why we all

have one head, two eyes, two arms, two legs, etc).Short tandem repeats (STRs) are used in forensic DNA

typing.STRs vary from person to person by the number of the

repeating sequences.

the repeat region is variable between samples while the flanking regions are constant

7 repeats

8 repeats

AATG

CSF1PO

D5S818

D21S11

TH01

TPOX

D13S317

D7S820

D16S539 D18S51

D8S1179

D3S1358

FGA

VWA

Location of13 CODIS Core STR Loci

AMEL

AMEL

Sex-typing

Process of Forensic DNA AnalysisDocument evidenceSample evidenceApply chemicals and

heat to separate the DNA from the rest of the cellular components

Purify DNADetermine

concentration of DNA

Actual AnalysisHours of on hands

sample manipulation

How much DNA?qPCR Instrument to

quantitate the DNA extract

Amplification of DNAPolymerase Chain

Reaction (PCR)Areas of DNA are

replicated millions of times.

Applied Biosystems 3130 Genetic Analyzer

DNA Analysis-hours at the computer!

Identifiler- 15 loci and amelogenin

Identifiler- 15 loci and amelogenin

Identifiler Tables

IDENTIFILER LOCI

Analysis continuedA report with a table of results is generatedThe laboratory work and report are technically reviewed

by a qualified analyst.The laboratory work and report are administratively

reviewed.Report is released.

Comparison of Genetic Profiles

Possible Outcomes of comparison of DNA Results to

Known Reference DNA profiles

•Inclusion (reference profile matches evidence profile)

•Exclusion (reference profile does not match evidence profile)

•Inconclusive (not enough information to make comparison)

Matching results from comparisonWhat is the significance of a match between the

reference profile and the evidence profile? Another way to think about this question is: How rare is the evidence profile in the population?

How rare is the evidence profile?First: Population StudyA study that counts how many times a certain allele is seen

for a genetic maker.The published data from the FBI is used for the 3 major

racial/ethnic groups (Caucasian, African American and Hispanic).

STR Allele Frequencies

0

5

10

15

20

25

30

35

40

45

6 7 8 9 9.3 10

Caucasians (N=427)

Blacks (N=414)

Hispanics (N=414)

TH01 Marker

*Proc. Int. Sym. Hum. ID (Promega) 1997, p. 34

Number of repeats

Per

cen

t

Conveying Frequency•A dice is six-sided. Therefore one in six= 1/6=0.1667.

•A 20-car parking lot full of cars, how many are blue? 5, 5 in 20= 5/20= 0.25

How rare is the evidence profile?Second: Apply StatistiMultiply the allele frequencies for each genetic marker.

Evidence

D3S1358

15 , 16

.24631 or 25% .23153 or 23%

(in Caucasians)

X = .11

How rare is the evidence profile?Second: Apply StatisticsMultiply the frequencies for each genetic marker together

to determine the overall frequency for entire the profile.

VWAD3S1358 FGA

.11

15, 16

D8S1179

16, 18 22,25 13, 15

.09 .03 .07X X X

Frequencies of 11 more genetic markers =

1 in # quadrillion,

15 zeros

Discrimination power of Identifiler

Population of Calif. and USA

World Population ~ 6.79 Billion

ConclusionThe evidence is presented and the strength of the match

conveyed.

We leave the decision of guilt or innocence for the jury to decide.