What is DNA Evidence?

DNA evidence involves the analysis of genetic material (Deoxyribonucleic Acid) to identify individuals.
DNA is unique to every individual (except identical twins) and can be found in body fluids (blood, saliva,
semen), hair, skin cells, and bones. This makes it a powerful tool for linking suspects to crime scenes or
determining familial relationships.

How DNA Evidence is Conducted:

1. Sample Collection: DNA samples are collected from crime scenes, victims, or suspects. This
includes blood, semen, hair follicles, skin cells, and other biological materials.

2. Extraction and Analysis: The collected samples undergo a series of processes:

o DNA Extraction: Isolating DNA from the sample.

o PCR Amplification: Polymerase Chain Reaction (PCR) is used to amplify the DNA to
obtain a sufficient quantity for analysis.

o Electrophoresis and Sequencing: The DNA is analyzed using gel electrophoresis and
sequencing techniques to create a profile.

3. Comparison: The DNA profile generated is compared to known profiles in a database or to the
DNA sample of a suspect or victim.

Who Conducts DNA Analysis?

 Forensic Scientists: Specialized forensic experts trained in genetics and molecular biology
conduct DNA analysis in certified forensic labs.

 Accredited Laboratories: Government forensic science laboratories (FSLs) and private DNA
testing labs certified by appropriate authorities.

Types of Cases Where DNA Tests Are Conducted:

1. Criminal Cases:

o Rape and Sexual Assault: To match DNA from the victim to that of the accused.

o Homicides and Violent Crimes: To link suspects to crime scenes through blood or other
biological material.

o Kidnapping and Missing Persons: For identification of bodies or linking evidence found
at a crime scene.

2. Civil Cases:

o Paternity Tests: To establish the biological father in family court cases.

o Inheritance Disputes: To prove biological relationships for inheritance claims.

o Immigration Cases: DNA testing may be required to prove familial relationships.

Who Can Request a DNA Test?

  Police/Investigating Agencies: Can request DNA testing as part of an investigation.

 Courts: A judge may order a DNA test during a trial or investigation.

 Prosecution and Defense: Both sides in a criminal case can request DNA testing to support their
arguments.

 Victims and Accused: May request DNA testing for exoneration or to strengthen their defense.

Technologies Available for DNA Testing:

 Polymerase Chain Reaction (PCR): Used for amplifying small DNA samples.

 Short Tandem Repeat (STR) Analysis: The most commonly used technique for DNA profiling.

 Mitochondrial DNA (mtDNA) Testing: Used for analyzing DNA in samples where nuclear DNA is
degraded or limited, such as old skeletal remains. This is particularly effective for maternal
lineage identification.

 Next-Generation Sequencing (NGS): A more advanced method that provides comprehensive

DNA sequencing.

Court Permission for DNA Testing:

 Court Approval: In India, court permission is generally required to conduct a DNA test, especially
if the accused does not consent. The Supreme Court in Selvi v. State of Karnataka (2010)
underscored the importance of consent for invasive tests.

 Criminal Identification Act, 2023: The act permits collection and testing of DNA samples from
accused individuals in cases involving offenses punishable by imprisonment of seven years or
more. This can be conducted with court oversight to ensure constitutional rights are upheld.

 Forceful Collection: Force cannot be used without legal authorization. If an accused refuses to
provide a DNA sample voluntarily, police must obtain a court order for the collection of such
evidence.

DNA Sample Durability and Preservation:

 DNA from Mixed Fluids: Advanced technologies like STR analysis can identify multiple DNA
profiles from a mixed sample.

 DNA from Dry Samples: DNA can be extracted from dried blood or other samples for several
years, depending on environmental conditions and preservation. Generally, DNA can be
preserved effectively for decades if stored properly.

 Preservation Conditions: The best and safest place to preserve DNA is in a controlled, sterile
environment at low temperatures (e.g., -20°C or lower).

 Long-Term Preservation: Properly preserved DNA samples can remain viable for analysis for over
20 years or more.
  Identical Twins: Identical twins share nearly identical DNA, making it challenging to differentiate
between them using standard DNA profiling. Advanced techniques like Single Nucleotide
Polymorphism (SNP) analysis may be used to identify subtle differences.

DNA in the Indian Population:

 Genetic Similarity: Approximately 99.9% of human DNA is similar across the population. The
0.1% variation is what makes each individual unique. The genetic diversity in India is
considerable due to its vast population and different ethnic groups.

Important Case Studies Involving DNA Evidence:

1. Nirbhaya Case (2012): DNA analysis was critical in confirming the identity of the perpetrators
and linking them to the crime.

2. Aarushi Talwar Case (2008): DNA evidence was used to examine the involvement of suspects,
although questions arose about contamination and reliability.

3. Priyadarshini Mattoo Case (2006): DNA profiling played a vital role in overturning the initial
acquittal and securing a conviction.

4. Jammu and Kashmir Kathua Case (2018): DNA evidence confirmed the presence of the accused
at the scene and was key in securing convictions.

5. Tandoor Murder Case (1995): One of the earliest cases in India where DNA evidence was used to
identify the victim's remains and link them to the accused.

Special Considerations:

 Female DNA Matching: Mitochondrial DNA (mtDNA) analysis is used for tracing maternal lineage
and is beneficial when nuclear DNA is degraded or limited.

 Mixed Fluid Analysis: Forensic experts can distinguish multiple DNA contributors in mixed
biological samples using STR analysis.

 Preservation Timeline: DNA can be extracted from dried blood samples for decades if stored in
optimal conditions. Proper preservation ensures the longevity of DNA samples, and they can be
used effectively for future analysis in reopened or cold cases.

DNA evidence is an invaluable tool for both criminal and civil cases in India. While it is conducted by
trained forensic experts and under strict regulations, court permission is typically required, especially
when involving the accused. DNA tests can provide reliable evidence that supports investigations, trials,
and verdicts. The technologies involved, such as STR and PCR, enable accurate profiling and long-term
preservation, ensuring that even old or degraded samples can be analyzed effectively.
Analyzing DNA from mixed biological fluids in cases involving an exceptionally high number of
contributors, such as 50 individuals, is extremely challenging and pushes the limits of current forensic
technology. Below, I provide an overview of the capacity for DNA profile separation in such cases for
India, the USA, and the UK, as well as which country currently has the best technology for this type of
analysis.

DNA Profiling Capabilities for Extremely Complex Mixtures:

1. India:

o Technology: India primarily relies on Short Tandem Repeat (STR) analysis, which is
effective for analyzing DNA with a small to moderate number of contributors. For
complex cases, some advanced laboratories may use probabilistic genotyping software,
though its use may not be as widespread or advanced as in other countries.

o Capacity: Indian forensic technology can reliably separate up to 3–5 distinct DNA
profiles. In highly specialized and well-equipped laboratories, this capacity can be
extended, but separating DNA from 50 contributors is beyond current capabilities.

o Limitations: For cases involving a high number of contributors (such as 50), the
technology available in India faces significant challenges due to the complexity and
overlap of genetic markers.

2. USA:

o Technology: The USA employs state-of-the-art DNA analysis technologies, including

STRmix, TrueAllele, and Next-Generation Sequencing (NGS). These probabilistic
genotyping software tools are specifically designed to handle complex mixtures and can
statistically separate DNA profiles from multiple contributors.

o Capacity: The USA's forensic labs are among the best equipped globally to handle
extremely complex mixtures. However, even with advanced technology, reliably
separating up to 50 distinct DNA profiles is challenging and would require significant
computational power and specialized expertise. Realistically, current technology may
handle up to 20–30 contributors with varying degrees of confidence.

o Best Practice: The USA is considered to have the most advanced capabilities for handling
complex DNA analysis due to its investment in technology and research.

3. UK:

o Technology: The UK also uses advanced DNA analysis methods, including STRmix and
TrueAllele, similar to the USA. The country has a robust forensic infrastructure and
experienced personnel.

o Capacity: The UK can handle complex DNA mixtures involving up to 20–30 contributors
reliably. Analyzing cases involving 50 contributors poses significant challenges, even with
the most advanced tools.
 o Expertise: The UK has world-class forensic laboratories capable of handling complex
cases, but separating profiles from 50 individuals would push current technological
limits.

Comparative Analysis:

 Best Technology for DNA Profile Separation:

o USA holds the lead due to its advanced technology and significant investments in
forensic research. Its use of probabilistic genotyping and deep sequencing methods
allows for more reliable separation of multiple DNA profiles from complex mixtures.

o UK follows closely with similar capabilities and a well-established forensic system.

o India has advanced its forensic capabilities significantly, but it is not yet at the level
required to handle cases involving the separation of DNA from 50 contributors with high
reliability.

Realistic Capabilities for 50 Contributors:

 USA: With the current state of technology, separating profiles from up to 20–30 contributors can
be done with relative confidence. Cases involving 50 contributors would require cutting-edge
research and extensive computational resources.

 UK: Similar to the USA, the capacity realistically extends to 20–30 contributors with the use of
probabilistic genotyping.

 India: Can typically manage up to 3–5 distinct profiles reliably, with potential for more in
specialized labs. Handling a mixture involving 50 contributors is currently beyond standard
forensic capabilities in India.

Key Techniques and Technologies:

 STR Analysis: Common in all countries but becomes less effective with a high number of
contributors due to overlapping alleles.

 Probabilistic Genotyping (USA and UK): Tools like STRmix and TrueAllele enhance the ability to
separate profiles in complex cases.

 Next-Generation Sequencing (NGS): Provides higher resolution and can identify more
contributors in a mixed sample.

Top Country for DNA Technology: The USA leads in DNA profiling for complex mixtures due to its
advanced use of probabilistic genotyping and comprehensive forensic resources.

 Limitations: Even in the USA and UK, analyzing biological fluid mixtures from 50 contributors
represents a significant technological and scientific challenge. The separation and identification
of DNA profiles from such a high number of contributors would require continued advancements
in technology and methodology.
  India: While India has improved its forensic capabilities, it would not currently be able to
separate and identify 50 individual DNA profiles reliably with existing technology.

In summary, while current forensic technology in the USA and UK can handle up to 20–30 contributors,
the challenge of accurately separating 50 DNA profiles from a mixed sample is beyond standard
practices and would require the most advanced technological solutions and further research.

Here are some significant cases in India where DNA

evidence played a crucial role in acquittals, convictions,
and resolving controversial cases:

1. Nirbhaya Case (Mukesh & Anr v. State for NCT of Delhi, 2017)

 Facts: The brutal gang rape and murder of a young woman in Delhi in 2012 shocked the nation.
The police collected biological samples from the victim and the accused.

 Role of DNA: DNA profiling was pivotal in linking the accused to the crime scene. The forensic
analysis matched the DNA found on the victim's body with samples taken from the accused.

 Outcome: The Supreme Court upheld the conviction and death sentences of the perpetrators.
The DNA evidence was critical in affirming their guilt and supporting the victim's statements.

2. Priyadarshini Mattoo Case (Santosh Kumar Singh v. State through CBI, 2006)

 Facts: Priyadarshini Mattoo, a law student, was raped and murdered in 1996. Santosh Kumar
Singh, who was initially acquitted due to lack of evidence and discrepancies in the investigation,
was later retried.

 Role of DNA: DNA evidence collected from the victim matched Singh's DNA profile, proving his
involvement.

 Outcome: The Delhi High Court convicted Singh, and the Supreme Court later upheld the
conviction, sentencing him to life imprisonment. DNA evidence was crucial in overturning the
initial acquittal and securing justice for the victim.

3. Tandoor Murder Case (State v. Sushil Sharma, 1995)

 Facts: Sushil Sharma, a politician, murdered his wife, Naina Sahni, and attempted to dispose of
her body by burning it in a tandoor. Initial identification of the body was difficult due to its
condition.

 Role of DNA: DNA profiling was used to confirm the identity of the victim as Naina Sahni. The
biological samples matched her known DNA, proving that the body was hers.

 Outcome: The DNA evidence supported the prosecution’s case, leading to Sharma's conviction
and death sentence (later commuted to life imprisonment by the Supreme Court).
4. Jammu and Kashmir Kathua Case (2018)

 Facts: An eight-year-old girl was raped and murdered in Kathua, Jammu and Kashmir, in a case
that drew national and international attention due to communal tensions. The investigation
involved multiple accused.

 Role of DNA: DNA profiling confirmed the presence of the victim’s blood in the prayer hall and
on the clothing of the accused. It also matched the DNA from the crime scene with that of the
main accused.

 Outcome: The DNA evidence was instrumental in convicting the main accused and others
involved. The trial court sentenced three of the accused to life imprisonment and three others to
five years in prison.

5. Aarushi Talwar and Hemraj Double Murder Case (2013)

 Facts: Aarushi Talwar, a teenager, and Hemraj, the Talwar family's domestic help, were found
murdered in their home. The case became one of India's most controversial due to media
attention and investigative lapses.

 Role of DNA: DNA evidence was used to analyze biological samples collected from the scene.
While the initial handling of evidence raised questions about contamination and reliability, the
court reviewed DNA findings as part of the investigation.

 Outcome: The Talwar parents were initially convicted based on circumstantial evidence but were
later acquitted by the Allahabad High Court in 2017, which cited insufficient evidence and the
prosecution's failure to prove their guilt conclusively. The DNA evidence's mishandling played a
role in undermining the case.

6. State of Maharashtra v. Chandrabhan Sudam Sanap (2015)

 Facts: In this case, Chandrabhan Sanap was accused of raping and murdering a young woman in
Mumbai. The victim’s body was found charred, complicating identification.

 Role of DNA: DNA analysis played a crucial role in linking Sanap to the crime through evidence
found on the victim's body and at the crime scene.

 Outcome: The DNA evidence was a key factor in securing a conviction. Sanap was sentenced to
death by the trial court, which was later confirmed by the Bombay High Court.

7. Madurai Bench of Madras High Court (Manjula v. State of Tamil Nadu, 2017)

 Facts: A murder case involving the accused, who was initially convicted based on circumstantial
evidence. The conviction was questioned due to lack of direct evidence.

 Role of DNA: DNA profiling provided crucial evidence that excluded the accused as the source of
biological material found at the crime scene.

 Outcome: The Madras High Court acquitted the accused, emphasizing the role of DNA in
confirming innocence when other evidence was inconclusive.
8. Swamy Shraddananda v. State of Karnataka (2008)

 Facts: The case involved the murder of Swamy Shraddananda's wife for financial gain. The
prosecution relied on circumstantial evidence supported by forensic findings.

 Role of DNA: DNA evidence corroborated the testimonies and other findings, confirming the
accused's involvement in the crime.

 Outcome: The conviction was upheld, and the Supreme Court noted the significance of forensic
evidence, including DNA, in supporting the prosecution's case.

Overview of the Role of DNA Evidence:

 Conviction: DNA has been pivotal in cases like the Nirbhaya, Priyadarshini Mattoo, and Kathua
cases, where it provided conclusive evidence linking the accused to the crime, leading to
convictions.

 Acquittal: DNA has also played a role in proving innocence, as seen in the Madurai Bench of
Madras High Court case, where DNA results helped overturn a wrongful conviction.

 Controversial Cases: Cases like the Aarushi Talwar double murder highlighted the importance of
proper handling and analysis of DNA evidence. Mishandling or contamination can undermine the
credibility of DNA evidence and impact the outcome.

Conclusion:

DNA evidence has proven to be a powerful tool in solving complex criminal cases, leading to both
convictions and acquittals. The Supreme Court and High Courts in India have relied on DNA profiling to
resolve cases that hinge on biological evidence. Proper handling, analysis, and presentation of DNA are
crucial for it to be reliable and impactful in court.