Forensic Science In Criminal Investigations
1. Introduction
Forensic science is the application of scientific methods and principles to investigate crimes and establish facts in legal proceedings. It encompasses multiple disciplines including:
DNA analysis
Fingerprint analysis
Ballistics and firearms examination
Toxicology
Digital forensics
Trace evidence analysis (hair, fibers, paint, etc.)
Purpose in Criminal Investigations:
Identify suspects through scientific evidence.
Establish links between the suspect, victim, and crime scene.
Corroborate or refute testimonies.
Determine the cause, time, and manner of death in homicide investigations.
Legal Basis:
Indian Evidence Act, 1872 – Sections 45–51 allow expert opinion evidence.
Criminal Procedure Code (CrPC) – Provisions for collection, preservation, and presentation of forensic evidence.
Internationally – Admissibility guided by Daubert standard (USA), requiring scientific validity.
2. Key Forensic Disciplines and Their Application
| Discipline | Application in Criminal Investigation |
|---|---|
| DNA Analysis | Identify suspects/victims, establish biological relationships |
| Fingerprints | Individual identification, linking suspect to crime scene |
| Ballistics | Determine firearm used, trajectory, distance |
| Toxicology | Identify poisons, drugs, cause of death |
| Digital Forensics | Recover deleted data, trace cybercrime activities |
| Trace Evidence | Connect suspect to scene via fibers, hair, paint |
3. Landmark Cases
A. State of Uttar Pradesh v. Rajesh Gautam (1998)
Facts: Accused implicated in murder based on circumstantial evidence.
Forensic Evidence: Fingerprints lifted from murder weapon matched the accused.
Held: Court relied heavily on fingerprint analysis to link the accused to the crime.
Principle: Properly collected and verified fingerprints are strong corroborative evidence.
B. Lillu @ Harish v. State of Karnataka (2005)
Facts: Homicide investigation with limited eyewitnesses.
Forensic Evidence: Bloodstains on clothing and footwear matched victim’s blood type and DNA profile.
Held: DNA and serological evidence provided scientific corroboration, strengthening conviction.
Principle: DNA profiling can independently establish involvement of the accused.
C. Selvi v. State of Karnataka (2010)
Facts: Involved sexual assault where victim identification was unclear.
Forensic Evidence: Semen samples subjected to DNA analysis, linking accused to the crime.
Held: Court emphasized that forensic evidence can compensate for weak eyewitness testimony.
Principle: Forensic evidence enhances accuracy and objectivity in criminal trials.
D. K. M. Nanavati v. State of Maharashtra (1962)
Facts: Famous murder case.
Forensic Evidence: Gunshot residue and ballistics analysis were used to determine shooting circumstances.
Held: Forensic reports helped reconstruct events and assess the plausibility of self-defense claims.
Principle: Ballistics and residue analysis are critical for establishing sequence and manner of crime.
E. State v. Rajesh & Ors. (Delhi High Court, 2007)
Facts: Large-scale narcotics seizure; accused claimed innocence.
Forensic Evidence: Chemical analysis of seized powders confirmed heroin and cocaine content.
Held: Scientific validation of substance critical for conviction under NDPS Act.
Principle: Chemical forensic analysis is essential in controlled substance cases.
F. R v. Doheny (UK, 1996)
Facts: Alleged murder with disputed DNA evidence.
Forensic Evidence: DNA profiling initially used; defense challenged reliability due to lab error possibility.
Held: Court stressed need for proper procedures, chain of custody, and lab verification.
Principle: Reliability and admissibility of forensic evidence depend on methodology and procedural safeguards.
G. State of Tamil Nadu v. Rajkumar (2013)
Facts: Cybercrime case involving online fraud.
Forensic Evidence: Digital forensics recovered deleted transactions and IP addresses.
Held: Court accepted digital forensic reports as primary evidence to identify accused.
Principle: Digital forensics is critical in modern criminal investigations, especially cybercrime.
4. Key Takeaways from Case Laws
Corroboration: Forensic evidence strengthens circumstantial or weak testimonial evidence.
Admissibility: Expert testimony under Sections 45–51 of Indian Evidence Act is essential.
Scientific Validation: Courts require that forensic procedures follow standardized, reliable methods.
Wide Application: From homicide and sexual assault to cybercrime and narcotics, forensic science is ubiquitous in criminal investigations.
Procedural Integrity: Maintaining chain of custody and lab accuracy is crucial for admissibility.
5. Summary
Forensic science ensures objectivity, accuracy, and reliability in criminal investigations.
DNA, fingerprints, ballistics, toxicology, and digital forensics are the cornerstones of evidence collection.
Case laws demonstrate its role in:
Identifying perpetrators (Rajesh Gautam, Lillu @ Harish)
Establishing sequence of events (Nanavati)
Confirming substance type in narcotics cases (Rajesh & Ors.)
Tracing cybercrime and digital fraud (Rajkumar)
Forensic evidence can tip the balance in criminal trials, especially when eyewitness evidence is limited.
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