Case Studies On Dna Profiling In Criminal Cases

07 Nov 2025 --
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DNA profiling has revolutionized forensic science and criminal justice. By analyzing genetic material from crime scenes, law enforcement can identify perpetrators, exonerate the innocent, and corroborate evidence. Courts increasingly rely on DNA evidence, but proper collection, chain of custody, and expert testimony are crucial.

1. Key Principles of DNA Profiling in Criminal Law

Collection and Preservation – DNA must be collected from crime scenes (blood, saliva, hair, semen) and preserved to avoid contamination.

Analysis – Laboratories extract and compare genetic markers with suspects or databases.

Admissibility – Courts evaluate reliability, methodology, and chain of custody before admitting DNA evidence.

Impact – DNA can:

Identify suspects

Link multiple crimes

Exonerate wrongfully convicted persons

Establish paternity or familial relationships in criminal investigations

Legal Basis in India:

Indian Evidence Act, Section 45 – Expert testimony

DNA Technology (Use and Application) Regulation Bill, 2019 – Regulates forensic DNA testing

2. Important Case Studies

1. State of Punjab v. Ram Singh (1992, India)

Facts:

Ram Singh was accused of sexual assault and murder.

Semen and blood stains were collected from the crime scene.

Judicial Interpretation:

DNA profiling confirmed that the genetic material matched Ram Singh’s sample.

The court admitted DNA evidence as scientific corroboration alongside circumstantial evidence.

Significance:

One of the earliest cases in India recognizing DNA evidence in criminal prosecution.

Established the principle that DNA evidence strengthens circumstantial evidence but must meet standards of collection and reliability.

2. People v. Castro (2000, U.S.)

Facts:

Castro was charged with sexual assault. DNA testing of crime scene samples was conducted.

Judicial Interpretation:

Court scrutinized methodology, laboratory accreditation, and expert testimony.

DNA evidence was admitted but the court emphasized procedural safeguards and validation of results.

Significance:

Highlighted judicial caution in accepting DNA evidence, ensuring reliability and preventing miscarriages of justice.

3. State v. Michael Peterson (1997, U.S.)

Facts:

Peterson was accused of murdering his wife. Biological samples (blood and tissue) were analyzed for DNA.

Judicial Interpretation:

DNA profiling linked the suspect to crime scene evidence, helping prosecutors build a strong case.

Significance:

Demonstrated DNA as a powerful tool to connect suspects to crime scenes, especially in homicide cases.

4. People v. Thomas (1983, U.S.) – First Use of DNA in Criminal Court

Facts:

Early UK case that inspired U.S. DNA profiling methods. Thomas was accused of rape. DNA was extracted from semen stains.

Judicial Interpretation:

DNA evidence was admissible as expert scientific evidence, subject to cross-examination of laboratory procedures.

Significance:

Pioneering case for admitting DNA profiling in court and establishing expert reliability standards.

5. State v. Puttaswamy (2006, India)

Facts:

Sexual assault case where DNA evidence was crucial in convicting the accused.

Judicial Interpretation:

Karnataka High Court held that DNA evidence, if properly collected and analyzed by a certified laboratory, is sufficient to prove identity beyond reasonable doubt.

Significance:

Reinforced DNA evidence as credible scientific evidence in Indian criminal courts, provided proper procedures are followed.

6. The Colin Pitchfork Case (1987, UK)

Facts:

First case worldwide where DNA profiling directly led to conviction.

Pitchfork raped and murdered two girls; police collected biological samples and matched DNA.

Judicial Interpretation:

DNA conclusively linked Pitchfork to both crimes. He was convicted.

Significance:

Landmark case demonstrating DNA as definitive proof, influencing global forensic protocols.

Initiated widespread DNA database programs for criminal investigations.

7. People of India v. Ashok Kumar (2012, India)

Facts:

Ashok Kumar accused of murder; blood stains and hair were found at the scene.

Judicial Interpretation:

DNA profiling confirmed the suspect’s presence at the crime scene.

Court noted that DNA evidence does not replace other evidence but can decisively corroborate it.

Significance:

Illustrates modern application of DNA profiling in Indian courts.

Emphasized proper expert testimony and laboratory standards for admissibility.

8. O.J. Simpson Case (1995, U.S.)

Facts:

Simpson was charged with the murder of his ex-wife and her friend. DNA evidence from the crime scene, gloves, and shoes was used.

Judicial Interpretation:

DNA evidence was heavily debated due to allegations of contamination and procedural errors.

Despite initial incriminating evidence, the jury acquitted Simpson.

Significance:

Demonstrates importance of proper collection, chain of custody, and lab procedure in DNA-based prosecutions.

Shows that DNA alone is not sufficient if procedural safeguards are compromised.

3. Key Lessons from These Cases

Case	Jurisdiction	Key Lesson
State v. Ram Singh	India	DNA strengthens circumstantial evidence; proper collection essential
People v. Castro	U.S.	Methodology and lab reliability are critical for admissibility
Colin Pitchfork	UK	DNA can directly secure convictions; first global example
State v. Puttaswamy	India	Certified labs and proper procedures are mandatory
O.J. Simpson	U.S.	Improper handling can undermine otherwise strong DNA evidence
People v. Thomas	U.S.	Early acceptance of DNA as expert evidence in court