Genetical Methods of Identification

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3. Introduction
 Types of identification:
1. Complete
2. partial
 identification means determination of individuality of a person.
 It is done in living person or dead by recognizing certain features or characteristics
that are unique that person.
1. Complete identification refers to the fixation of the individuality of a person.
2. Partial identification implies ascertainment of only some traits or characteristics
regarding the identity.
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In living persons
Medicolegal importance:
In dead persons

4. Medicolegal importance
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In living persons
B. Criminal casesA. Civil cases
1.Identification of accused in criminal
offenses of assault, murder, dacoity,
sexual offenses etc.
2. Absconding soldiers
3. Interchange of new born babies in
hospital
4. Criminal abortion
5. To fix-up age of criminal responsibility
and majority
6. Impersonation in criminal cases.
1.Impersonation or false personation cases
relation with
•Inheritance of property
•Pension
•Life insurance
•Voting rights
•Passport
2. Disputed identity in cases of divorce or
nullity of marriage
3. Disputed sex
4. Missing person
5. Lost memory patients

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In Dead Persons:
Identification is important to identify the individuals who died in mass disaster, air-
crash accidents, fire victims, exhumation, explosion and bomb-blast injuries,
mutilated and decomposed bodies and in skeletal remains.
Medicolegal importance
Data
Data for identification consist of: 1. Religion 2. Race 3. Sex 4. Age 5. Stature
6. Dactylography 7. Foot prints 8. Cheiloscopy 9. Tattoo marks 10. Scars
11. Deformities 12. Anthropometry 13. Teeth 14. DNA typing 15. Blood group and
HLA typing 16. Miscellaneous data

6. DNA typing
Introduction
 DNA profiling is also called as DNA fingerprinting, DNA typing
 The application of DNA technology to forensic medicine is the most remarkable
recent advances in forensic identification.
 In DNA profiling, DNA extracted from the sample is analyzed. DNA profiles are
unique to each individual except in monozygotic twins.
 Alec Jeffreys in 1984 discovered unique application of RFLP technology to
personal identification and labeled it as DNA fingerprinting akin to fingerprinting
 The chances that DNA profiles in two individuals are similar are about 1 in 30
billion to 300 billion i.e. half the population of world.
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7. Application of DNA profiling
1. To establish identity of a person in: • Sexual crimes – rape/sodomy/buccal coitus
• Violent crimes – murder • Accidents/ mass disaster • Missing person • War fighters
• Baby mix-ups • Amnesia/disabled person • Mistaken identity.
2. To acquit a falsely implicated person from such similar: crime.
3. Identification in postmortem practice: • Accidents • Disasters • Decomposition • Mutilated remains
• Skeleton • Exhumation • In embalmed tissues.
4. Disputed paternity
5. Disputed maternity.
6. To resolve disputes of: • Adultery • Incest • Child born out of rape cases
• Custody of a child born out of wedlock • False implication on a person being father of a certain child.
7. Extortion cases.
8. Immigration cases.
9. Determination of twin zygosity.
10. To identify sex
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Common evidentiary material and sources found at scene of crime
Sources of DNAEvidence/material
Blood, hair, tissue
Blood, tissue
Blood, semen, sweat
Saliva
Saliva
Semen, vaginal cell, penile cell, hairs
Saliva
Tissue, blood
Weapons
Bullet
Clothes
Toothbrush
Used cigarette/butts
Used condom
Bite mark
Finger scrapings/content

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DisadvantagesAdvantages
1. Susceptible to contamination1. Require only trace amount of DNA
2. Procedure is fast and requires less time
3. Highly sensitive method.

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STR is done by:
1. Isolating the DNA
2. Replicating the STR fragments by PCR
3. Performing gel Electrophoresis
4. Identifying the fragments using stains or laser technique.

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1. DNA profiling cannot differentiate between monozygotic twins
2. Expensive
3. Interpretation requires trained manpower
4. Susceptible for contamination.
1. Conclusive method of identification of an individual
2. Method can be applied to old stains or biological material
3. Small quantity of sample is required.

21. DNA typing
1. Non-human DNA
2. Degradation of sample
3. Contamination of sample
4. Multiple contributors to sample.
1. Sample contamination with genomic DNA from environment
2. Contamination between samples during preparation
3. Contamination of a sample with amplified DNA from previous reaction.
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