DNA analysis is a cornerstone technique in forensic science, used to identify individuals and establish genetic relationships. It involves extracting DNA from biological samples found at crime scenes, such as blood, hair, saliva, or skin cells, and comparing it to known samples, like those from suspects or victims.

2. Title: Process of introduction DNA
Name :- Rohan Singrore
Institution :- SAM School of science
Date :- 8 April 2024

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 bind to a complementary DNA sequence in
the sample

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 partial fingernail, which could
contain scraped-off

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
profile.

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 After Trial,
1996).

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 2 of those years on death row (

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, theft and drug crimes. With DNA evidence, the
average crime cleanup rate increases from 24 per cent to 43 per cent

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