The methods for producing a DNA profile were developed by Alec Jeffreys and his team in 1985. Jefferys discovered that an unknown sample of DNA such as blood, hair, saliva, or semen could be analyzed and a unique DNA pattern/profile could be developed. DNA analysis was first discovered, a process called Restriction Fragment Length Polymorphism (RFLP) was used to analyze

1. Rohan Singrore

2. Process of introduction
Of DNA

3. What is DNA analysis?
• DNA analysis is an examination method
that emerged in the mid 1980’s by Alec
Jefferys, an English geneticist.
Date :- 8 April 2024

4. How Does it work?
• Any organism can be identified by examination
of DNA sequences unique to the specific
species.
• To identify individuals, forensic scientist
scan 13 DNA regions (loci) and create a DNA
profile for that individual (DNA finger print)
• There’s a very slim chance that another
individual has the same DNA profile for a
specific set of 13 loci’s.

5. How is DNA typing done?
• Only 1/10 of a single percent of DNA (about 3
million base pairs) differs between
individuals.
• Scientist use these regions to generate a DNA
profile of an individual using samples from
blood, bone, and hair.
• In criminal cases, samples are collected from
the crime scene evidence, and a suspect,
extracting DNA and analyzing it for a set of
specific DNA markers
• Markers are found in DNA by making small
pieces of DNA (probes) that will seek out and

6. DNA Typing Cont’d
• The DNA profiles are then compared to determine
if the suspect sample matches the evidence
sample
• If the sample profiles do not match, the
suspect was not part of the crime
• If the patterns match the suspect most likely
was a part of the crime
• The more probes used in DNA analysis, the
greater the odds for a unique pattern and
definite match. Four to six probes are
recommended.

7. DNA Technology
• The DNA types stored in this system consist of
stretches of a chromosome that are highly
variable between individuals. These are usually
STR tetramers, or a sequence of four
nucleotides which repeats many times.

8. DNA as Evidence
• DNA is easily contaminated due to the
sensitivity and fragility of samples
• Must be recognized that the issue of DNA
contamination was not fully understood in the
past, older cases may be linked to samples
which could yield misleading results
• Many guidelines for handling DNA samples within
the lab before, during, and after processing

9. DNA as Evidence
• Degradation is also a common concern with DNA
samples Collection and storage must be
carefully monitored to prevent bacteria growth
• Evidence collected for the purpose of blood
type testing may be stored according to that
type of test and may limit chances of testing
DNA in the sample
• In some cases, DNA has been successfully
extracted and analyzed from a moldy sample with
the help of PCR technology

10. Laws related to DNA Technology
• With the recent advancements in DNA, many laws
have been issued in regards to testing and use
• Although DNA samples can last many years, and
sometimes even decades, statutes of limitation
are in place and vary state to state
• A statute of limitation limits the amount of
time between a crime and a conviction
• Many law makers are now realizing that theses
statutes of limitation are becoming obsolete
due to the reliability of a properly stored DNA
sample

11. Laws related to DNA Technology
• With the realization that DNA databases lead
to convictions, laws were put in place to
ensure their continued success
• All states require at least some convicted
offenders to provide a DNA sample to
incorporate their profile into the database
• Federal government now requires samples from
those convicted of Federal or military crimes

12. Equipment for DNA Analysis
• Thermocycler- also known as a thermal cycler,
it is used to amplify segments of DNA via PCR
• ABI 310 Genetic Analyzer- used for STR
genotyping

13. DNA Techniques

15. DNA ANALYSIS
• DNA analysis consists of traditional and
specialized techniques.Traditional Techniques:
Restriction fragment length polymorphism
(RFLP), and short tandem repeat (STR)
analysis.Specialized Techniques: mitochondrial
DNA (mtDNA) analysis, Y-marker analysis, single
nucleotide polymorphism, or SNP.

16. (RFLP) Restriction fragment
length polymorphism

18. Now What?
• Now compare questioned sequence to known
sequence.

19. DNA Matching History,
Collection and Databases

20. Brief History of DNA Matching
• 1970s-HLA TestingHLA inherited from both
parents. Used for paternity testing and
biological relationships. High exclusion rate
of 80%
• 19805- DNA Testing Using RFLP Technique First
genetic test using DNA. Higher exclusion rate
of 99.99%
• 19905 - DNA Testing Using PCR Technology DNA
tests made more easy and quick
• 2007s and beyond - Ancestry ResearchY-STR and
mtDNA used for male and female line
respectively

21. Admissibility of DNA Evidence
In American Courts
• November, 1987 - Tommy Lee Andrews was one of
the firsts convicted using DNA tests. Rape
Conviction
• State v. Woodall - West Virginia Supreme Court
first high court to rule on the admissibility
of DNA evidence
• People vs. Castro - Court certifications,
accreditations and standardization guidelines
were established (Chain of Custody in Courts)

23. Chain of Custody
• Used to make sure DNA samples is not
contaminated. Proper paperwork required
for court proceedings
• DNA collected by third party laboratory
professionals.
• Gloves are worn and caution is observed
• DNA is collected and sealed in a
specially made package
• Receiving lab will first check to make
sure the package is sealed before
proceeding to work on the DNA

24. DNA Collection
• A weapon, such as a baseball bat, fireplace
poker or knife, which could contain sweat,
skin, blood or other tissue
• A hat or mask, which could contain sweat, hair
or dandruff
• A facial tissue or cotton swab, which could
contain mucus, sweat, blood or earwax
• A toothpick, cigarette butt, bottle or postage
stamp, all of which could contain salivaA used
condom, which could contain semen or vaginal or
rectal cellsBed linens, which could contain
sweat, hair, blood or semenA fingernail or

25. DNA Matching
• 1.Inclusions, in which the
suspect DNA matches that of
the DNA profile taken from
the crime scene.
• 2. Exclusions, in which the
suspect DNA does not match
that of the DNA profile taken
from the crime scene.
• 3.Inconclusive results,
results from possible
contamination of evidence,
and or DNA may be very small
or degraded and cannot
produce an accurate DNA

26. Exoneration

27. Exoneration
• A person previously convicted of a crime is
later found to be innocent of that crime
• DNA testing of evidence has become the most
common method of post conviction exoneration of
the wrongfully accused.
• In the first 225 DNA evidence exonerations, 77%
of the exonerated persons were convicted due to
eyewitness misidentification (Innocent
Project).
• Most of the exonerated persons were convicted
of rape and sexual assault (Convicted By
Juries, Exonerated By Science: Case Studies in
the Use of DNA Evidence To Establish Innocence

28. Common Causes of wrongful
conviction
• Eyewitness misidentification
• Invalid or improper forensic science
• False confessions
• Government misconduct
• Informants / snitches
• Bad lawyering

29. David Vasquez
• ■ The first convicted defendant to be
exonerated by DNA evidence testing in 1989 in
Virginia
•
• • Wrongfully convicted of sexually assaulting
and hanging a woman in her Arlington County,
Virginia home and was sentenced to 35 years in
prison
•
• • Convicted because two witnesses placed him
near the scene of the crime (EYEWITNESS
MISIDENTIFICATION), and he plead guilty because
of he dreamt that he committed

30. David Vasquez cont’d
• Three laboratories conducted DNA testing on
this case and other similar cases that involved
the same sexual assault and murder methods that
were used in this particular case and found the
pubic hair from the scene of the crime
inconclusive with Vasquez’s.
• Exonerated in 1989 after having served 5 years
of his sentence

31. Kirk Bloodsworth
• The first convicted defendant exonerated from
death row through post conviction DNA testing
• Wrongfully convicted of the rape and brutal
beating / murder of a 9 year old girl and
sentenced to two consecutive life terms
• Convicted because of an anonymous call and 5
eyewitnesses saying that Bloodsworth was seen
with the girl earlier that day, a witness
identifying him through a police sketch
(EYEWITNESS MISIDENTIFICATION), and he admitted
to doing something terrible that day, as well
as mentioning a bloody rock

32. Kirk Bloodsworth cont’d
• Forensic Science Associates, the laboratory
that conducted the DNA testing, performed
Polymerase Chain Reaction (PCR) testing using
reference blood samples from the victim and
Bloodsworth.
• They found that the DNA from a semen stain
found in the victim's panties did not match any
of the DNA collected from the samples,
therefore Bloodsworth was excluded from this
crime.
• Exonerated in 1993 after having served almost
9years of his double life sentence and spending

33. DNA Data Bases
The development and expansion of databases that contain
DNA profiles at the local, State, and national levels
have greatly enhanced law enforcement's ability to solve
cases with DNA.
• Convicted offender databases store hundreds of
thousands of potential suspect DNA profiles, against
which DNA profiles developed from crime scene evidence
can be compared.
• Given the recidivistic nature of many crimes a
likelihood exists that the individual who committed the
crime being investigated was convicted of a similar
crime and already has his or her DNA profile in a DNA
database that can be searched by the Combined DNA Index
System (CODIS) software
• In a typical month, the database churns out hits for 15
murders, 45 rapes and sexual offences and 2500 car,

34. Case Study

35. Case Study: Familial DNA
• Familial searching is the use of
family members’ DNA to identify a
closely related suspect in
jurisdictions where large DNA
databases exist, but no exact
match has been found.
• LA police arrested the serial
killer “Grim Sleeper”
• Accused of killing 11 people,
dating back to 1985
• Compared DNA from crime scene with
suspects son (in LA Lock-up)
Franklin had for a
time, worked as a
garage attendant at a
Los Angeles police
station and previously
had an arrest record
although his offenses
did not require him to
submit a DNA sample

36. Controversy
• Justice For All Act
CODIS was once reserved for those convicted
of violent offences, but now states can
upload profiles of almost anyone charged
with a crime.
• Police are given the authority to
collect DNA from any person
arrested on suspicion of a
“recordable offence”.These are
people who may never have been
charged, let alone convicted.
• The best argument for including
innocent people’s profiles on the
database is, of course, that it
gets results
• If your DNA is on the
database it means that
you are forever an
automatic suspect for any
crime in the future. It
undermines the principle
of presumptive innocence.
• Being listed could
jeopardize employment or
foreign travel, and the
information could be used
for research on topics
such as the genetic
correlates of ethnicity
or criminal behavior

37. How Do You Feel About DNA Data
Bases, And Using Familial DNA?
Is It A Violation Of Privacy?

38. Exonerating The Wrongly
convicted
• In February 1987, in
Houston, Texas, a
fourteen-year-old girl
was forced into a car by
two Latino men. She was
taken to a house where
both men raped her. After
the sexual assault, she
was placed in the car
again and left on a
roadside.
• A man who served 17 years in prison for a rape
he did not commit was formally declared
innocent after DNA tests ruled out his guilt
• George Rodriguez was cleared of all wrongdoing
• Prosecutors say DNA tests rule out his
participation in the 1987 rape
A hair found in the
victim’s underwear
was said to be
microscopically
similar to the hair
standard from George
Rodriguez

39. Effectiveness of DNA
• DNA Identification is quite effective when used
correctly.
• Portions of DNA sequence that vary the most
among humans MUST used
• Portions must also be large enough to factor
in the fact that human mating is not absolutely
random

40. Examples of use of DNA In
forensics
• Identify potential suspects whose DNA may
match evidence left at crime scene
• Exonerate persons wrongly accused of crimes
• Identify crime and catastrophe victims
• Establish paternity and other family
relationships

41. DNA Technology
• CODIS, which stands for Combined DNA Index
System, is a program which consists of many
databases that have DNA profiles useful for the
criminal justice system
• The NDIS, or National DNA Index System, is the
part of CODIS that contains the DNA profile at
a national, state, and local level and is
accessible to law enforcement all over the
country

43. •Thank you
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