Forensic Science Notes PDF

UNIT1 Introduction to Forensic Science Forensic science is the application of scientific knowledge to legal problems and criminal investigations. While forensic science might seem like a modern development, its roots extend deep into history. Evidence, whether biological, chemical, or physical, bec...

UNIT1 Introduction to Forensic Science Forensic science is the application of scientific knowledge to legal problems and criminal investigations. While forensic science might seem like a modern development, its roots extend deep into history. Evidence, whether biological, chemical, or physical, becomes a crucial tool for investigators and is often the deciding factor in court trials. Forensic science uses various reliable, sensitive, and accurate techniques to analyze this evidence, such as DNA analysis, fingerprinting, ballistics, and toxicology. These techniques help investigators solve cases where human observation might be insufficient or unreliable. Key Historical Examples:  Marie Lafarge (1840): Convicted of murdering her husband using arsenic, this case was one of the first where forensic toxicology was applied to determine the cause of death.  Francisca Rojas (1892): This was the first murder case solved using fingerprint evidence. It marked the beginning of the use of fingerprinting in criminal investigations.  Tandoor Murder Case (1995): The victim, Naina Sahni, was identified through DNA analysis, showcasing the critical role of forensic science in modern investigations. Definition: Forensic science is a multidisciplinary field that applies various branches of science, such as physics, chemistry, biology, and engineering, to matters of law and criminal investigation. It provides answers to questions like:  How did the blood get to a specific location?  Is the blood toxic, and to whom does it belong? By using science in the service of justice, forensic science helps reconstruct crimes, identify perpetrators, and ensure fair trials. History and Development of Forensic Science The development of forensic science has been shaped by contributions from various scientists and historical milestones. It can be divided into two parts: contributions from other countries and contributions from India. Each period has witnessed the introduction of critical forensic techniques that have transformed the field into the modern scientific discipline it is today. A. Contributions from Other Countries The evolution of forensic science owes much to the early work of scientists and legal scholars worldwide. Here are some key figures and their contributions: 1. Mathieu Orfila (1814): o Known as the father of forensic toxicology. o Published the first scientific treatise on the detection of poisons and their effects on animals. o His work laid the foundation for toxicology as a scientific discipline in criminal investigations. 2. Alphonse Bertillon (1879): o Developed the first scientific system for personal identification, known as Anthropometry. o This system measured and recorded the dimensions of the human body and was used until fingerprinting replaced it. 3. Francis Galton (1892): o Conducted the first scientific study of fingerprints and developed a classification system for them. o His work proved that fingerprints are unique and consistent throughout life, making them a reliable form of personal identification. 4. Hans Gross (1893): o Published "Criminal Investigation," the first textbook on the application of scientific principles to criminal investigation.  o His work is considered a foundation for modern criminalistics. 5. Dr. Leone Lattes (1915): o Developed a simple procedure to determine the blood group from dried bloodstains, revolutionizing blood analysis in criminal cases. o This method was applied to numerous criminal investigations and remains a cornerstone of forensic serology. 6. Calvin Goddard (1925): o Pioneered the use of the comparison microscope in ballistics. o His work enabled investigators to link bullets and cartridge cases to specific firearms. 7. Albert S. Osborn (1910): o Authored the book "Questioned Documents", which established fundamental principles for the examination of documents in legal contexts. o His work formed the basis for forensic document examination, including handwriting analysis. 8. Edmond Locard (1910): o Known for Locard’s Exchange Principle, which states, "Every contact leaves a trace." o This principle became a cornerstone of forensic investigation, emphasizing that criminals inevitably leave physical traces at crime scenes. B. History and Development of Forensic Science in India Forensic science in India has a long and rich history, with its roots dating back to the colonial period. The country has made significant contributions to the development of forensic science, both before and after independence. Pre-Independence Milestones: 1. 1853:  o The first Chemical Examiner's Laboratory was established in Kolkata. o It was primarily used to analyze chemical substances, especially in poisoning cases. 2. 1897: o The world's first Fingerprint Bureau was established in Calcutta. o This pioneering step by India became a global model for fingerprint identification. 3. 1864: o A Chemical Laboratory was set up in Agra, expanding the forensic infrastructure in the country. 4. 1870: o A Chemical Laboratory was established in Mumbai, further enhancing forensic capabilities in Western India. 5. 1948: o The first Chemical Laboratory in Madras (now Chennai) was established, continuing the development of forensic services. 6. 1892: o Anthropometric Bureau established in Kolkata, focusing on physical measurements of criminals to aid in their identification, based on Bertillon’s anthropometry system. Post-Independence Milestones: 1. 1952: o India’s first Forensic Science Laboratory (FSL) was established in Calcutta (now Kolkata), paving the way for modern forensic investigations. 2. 1955: o The Central Fingerprint Bureau was set up in India to maintain and analyze fingerprint records, centralizing this crucial forensic practice.  3. 1957: o The first Central Forensic Science Laboratory (CFSL) was established to provide forensic services at the national level, setting a benchmark for state- level labs. 4. 1959: o The first educational institute for forensic science was established at Dr. Harisingh Gour University, Sagar, Madhya Pradesh, marking the beginning of forensic science education in India. 5. 1970: o The Bureau of Police Research and Development (BPR&D) was established in New Delhi to enhance forensic research and police training in India. 6. 1972: o The National Institute of Criminology and Forensic Science (NICFS) was established in New Delhi, serving as a central training institute for forensic and criminology professionals. 7. 1998: o The Centre for DNA Fingerprinting and Diagnostics (CDFD) was established in Hyderabad, making DNA analysis and fingerprinting more accessible in criminal investigations. Key Developments and Contributions: 1. Fingerprinting and Document Examination: India played a pivotal role in the establishment of fingerprinting as a global forensic technique, starting with the first Fingerprint Bureau in Calcutta (1897). 2. Forensic Education and Research: The establishment of dedicated forensic science laboratories and institutes in the post-independence period has significantly contributed to the education and training of forensic experts, making India a leader in forensic research in Asia.  3. Introduction of Modern Techniques: The development of forensic DNA analysis, ballistic examination, and toxicology divisions in India after the establishment of central and regional forensic science laboratories has modernized the country’s criminal investigation techniques. 4. Government Support: Post-independence, the Indian government has played a major role in promoting forensic science through the establishment of various forensic laboratories and institutes that continue to play a key role in solving crimes across the country. The Need for Forensic Science Forensic science plays a vital role in solving crimes scientifically. As criminals become more sophisticated, forensic methods become even more crucial in bringing justice. In the absence of forensic science, cases could rely solely on witness testimony, which is often unreliable due to biases, memory lapses, or emotions. Forensic evidence is scientific, reproducible, and devoid of human flaws, making it a more reliable way to solve crimes. Importance of Forensic Science:  Protection of the Innocent: Forensic science ensures that the innocent are not wrongfully convicted, as physical evidence can eliminate suspects who were not involved.  Conviction of the Guilty: Solid forensic evidence is often the linchpin in securing a conviction, as it links the suspect to the crime, the victim, or the crime scene.  Scientific Methodology: Investigators use scientific methods, free from human emotions or biases, to uncover the truth in a crime.  Every Contact Leaves a Trace: The principle of exchange, or Locard’s principle, ensures that criminals leave behind trace evidence (hair, fibers, fingerprints, etc.), even if they attempt to avoid detection. Objectives of Forensic Science The primary goals of forensic science are:  1. Determining if a Crime Occurred: In cases like unexpected deaths, forensic science helps determine whether foul play was involved or if it was a natural event (e.g., distinguishing murder from a heart attack). 2. Reconstructing the Crime: Forensic evidence can help identify how, when, and where the crime was committed, providing a clear picture of the sequence of events. 3. Identifying the Perpetrator: By analyzing physical evidence such as fingerprints, DNA, or fibers, forensic experts can link the crime to the suspect. 4. Establishing Links Between Victims, Suspects, and Crime Scenes: Forensic science helps connect the different aspects of a crime, such as linking a suspect to the weapon or location. 5. Distinguishing Real from Staged Crime Scenes: Some crimes may involve staged crime scenes to throw off investigators. Forensic experts can detect signs of tampering or staging. 6. Providing Objective, Reliable Evidence: Forensic evidence is verifiable and reproducible, making it an essential tool in court to convict the guilty and exonerate the innocent. Branches of Forensic Science Forensic science covers many specialized areas, each focusing on different types of evidence or analysis. Some of the key branches include: 1. Forensic Medicine: The application of medical knowledge in legal cases, often involved in determining causes of death. 2. Forensic Anthropology: Identifying human skeletal remains to determine age, sex, height, and sometimes the cause of death. Forensic anthropologists often assist in mass disaster situations. 3. Forensic Chemistry: Analyzing chemical substances, such as drugs, explosives, and toxins, to determine their composition and potential use in crimes. 4. Forensic Biology: Examining biological materials (blood, saliva, semen) to establish connections between the crime and individuals involved. This includes subfields like:  o Forensic Botany: Using plant evidence (like pollen or seeds) to link suspects to crime scenes. o Forensic Entomology: Studying insects found on corpses to determine the time since death. o Forensic Odontology: Analyzing dental evidence (e.g., bite marks) for identification or to link a suspect to a crime. o Forensic Serology: Identifying individuals through bodily fluids. 5. Forensic Physics: Using physics to analyze physical evidence such as glass, soil, and fibers. 6. Forensic Pathology: Investigating unnatural deaths through autopsies, determining causes such as injury, poisoning, or trauma. 7. Forensic Toxicology: Analyzing body fluids to detect the presence of drugs or poisons. 8. Forensic Taphonomy: Studying the decomposition of bodies to understand post- mortem processes and environmental effects on a corpse. 9. Forensic Engineering: Investigating structural failures, such as building collapses, to determine whether the failure was accidental or intentional. 10. Forensic Psychiatry: Studying the psychological state of individuals involved in legal proceedings to determine their fitness to stand trial or the mental state at the time of the crime. Scope of Forensic Science Forensic science offers numerous career paths in both the government and private sectors. Professionals in forensic science can work in the following areas: A. Government Sector:  Forensic Science Laboratories (FSL): Experts analyze physical evidence at the state or central level.   Law Enforcement Agencies: Forensic experts assist police, CID, CBI, and other agencies in solving crimes.  Educational Institutions: Many forensic scientists work as educators, training the next generation of investigators.  Research & Development: Forensic scientists develop new techniques and methods to improve forensic analysis. B. Private Sector:  Private Detective Agencies: Forensic scientists work in private investigative agencies solving cases for private clients.  Insurance Companies: Investigating fraud or claims involving accidents or injuries.  Private Laboratories: Providing analysis for private investigations or legal cases.  7. Conclusion  Forensic science is an essential tool in the criminal justice system, helping to ensure that the guilty are convicted and the innocent are exonerated. It bridges the gap between science and law, providing courts with objective, reliable, and scientifically validated evidence. This multidisciplinary field not only aids in solving crimes but also helps in understanding complex legal cases by providing detailed analyses based on scientific principles.  As technology advances, forensic science continues to evolve. Techniques such as DNA profiling, digital forensics, and advanced chemical analyses have revolutionized the field, allowing investigators to solve crimes that were once considered unsolvable. However, forensic science is not static. Continuous education and research are essential for forensic professionals to stay updated with the latest advancements and ensure that justice is served.  For students and professionals entering the field, it’s important to understand the underlying principles, methodologies, and ethics that guide forensic work. With the rapid growth in crime rates and the complexity of criminal activities, the demand for forensic expertise will only increase, offering immense opportunities for those looking to contribute to the field of criminal justice. Basic Principles of Forensic Science: 1. Law of Exchange (Locard's Principle) This principle was introduced by Edmond Locard, a pioneering French forensic scientist. Locard’s Exchange Principle states, "Every contact leaves a trace." This means that when two objects come into contact with each other, there is always an exchange of materials. In the context of forensic science, this exchange can occur between a perpetrator, the victim, and the crime scene. This exchange could include traces such as:  Fingerprints: Left by the perpetrator or victim on surfaces like doors, weapons, or glass.  Hair: Strands of hair that fall off during physical contact or movement.  Fibers: Fabric from clothing might transfer to a suspect or scene.  Soil or dust particles: Shoes or tools can carry soil or particles from the crime scene to the perpetrator’s location or vice versa. This principle is crucial in crime scene investigation because it allows forensic scientists to find physical evidence that can link the suspect to the crime. The ability of investigators to collect these traces depends heavily on their skills and knowledge. For example, in a murder case, an investigator might find a perpetrator’s fingerprints or blood at the scene, and they might unknowingly take soil or grass from the scene with them. 2. Principle of Individuality The Principle of Individuality states that every object, whether natural or man-made, is unique. No two objects or living things are exactly alike, not even identical twins or leaves from the same branch of a tree. This uniqueness is a fundamental aspect of forensic science. In forensic investigations:  Fingerprints: No two individuals, not even identical twins, have the same fingerprints. Fingerprint analysis is, therefore, a powerful tool for identifying individuals.  DNA: While DNA from identical twins is extremely similar, small differences can still be detected in their fingerprints or other biological markers.   Manufactured items: Objects like coins, firearms, and tools have unique features. Even items produced in the same batch or factory show slight differences. For example, during the manufacturing of firearms, each gun receives individual characteristics (microscopic striations on the barrel) that make it different from another. This principle helps forensic experts identify suspects or objects associated with a crime based on their unique features. 3. Law of Comparison The Law of Comparison is based on the premise that only "like can be compared with like." For example, blood found at a crime scene can only be compared to human blood, not animal blood. Similarly, hair from a crime scene must be compared with human hair if the goal is to link it to a person. This principle is vital for proper forensic analysis:  Blood analysis: If an investigator recovers human blood at a crime scene, it would be inappropriate to compare it with animal blood. Such a comparison would yield no useful results.  Tool marks: If a tool mark is found at a burglary scene, it should be compared to similar types of tools, not dissimilar objects like knives or screwdrivers. The analysis of like items is necessary for accurate identification. Forensic scientists follow this principle to ensure the accurate analysis and interpretation of evidence, avoiding incorrect or irrelevant comparisons. 4. Principle of Linkage The Principle of Linkage refers to the idea that physical evidence found at a crime scene can create connections between different elements of the crime:  Suspect to Victim: Evidence like fingerprints, DNA, or hair can directly link a suspect to the victim.  Suspect to Crime Scene: Physical evidence such as clothing fibers or soil on a suspect’s shoes can link them to the crime scene.   Victim to Crime Scene: Traces like blood, personal items, or body fluids found at the crime scene link the victim to that location. Linkage is an essential concept for solving crimes, as it provides a means of proving or disproving a suspect’s involvement. For example, if a suspect leaves a personal item like an identity card at the scene, it provides strong physical evidence linking them to the crime. The physical evidence is usually more reliable than verbal testimony, as people may lie, but the evidence often does not. 5. Law of Probability Probability in forensic science is used to assess how likely it is that a particular event or outcome is related to a crime. It helps forensic scientists quantify the likelihood that the evidence collected is connected to the suspect or event. For example:  DNA evidence: The probability that a DNA sample found at the crime scene belongs to a specific individual can range from 90% to 99.99% or even 100%, depending on the quality of the sample.  Likelihood of events: Investigators might use probability to estimate which of several gangs could be responsible for a robbery based on physical evidence, witness reports, and historical patterns. This law assists forensic experts in determining the strength of the connection between a suspect and the evidence. Probability is a mathematical concept that helps investigators assess the certainty or uncertainty of a particular event or result. 6. Law of Progressive Change The Law of Progressive Change states that everything changes over time. In forensic science, this principle is particularly important because physical evidence does not remain in its original state indefinitely. It may degrade, decompose, or become contaminated over time. Some examples of progressive change in forensic investigations include:  Biological evidence: Blood, saliva, or other bodily fluids may degrade if not properly preserved, making analysis more difficult or less reliable.   Crime scene alterations: Environmental factors, such as weather or human activity, can change a crime scene over time. For example, rain could wash away trace evidence, or a person might unknowingly disturb a crime scene, altering crucial evidence.  Perpetrator characteristics: Over time, the physical appearance of a suspect may change, making it more difficult for witnesses to identify them. This principle highlights the importance of acting quickly and correctly to preserve evidence. If evidence is not collected and preserved in a timely manner, it may lose its forensic value, leading to potentially inaccurate conclusions. 7. Law of Analysis The Law of Analysis emphasizes that "the analysis can be no better than the sample analyzed." This means that the quality and accuracy of forensic analysis are directly related to the quality of the evidence collected. If the evidence is not properly collected, preserved, or transported, the results of any forensic analysis may be compromised. For example:  Contamination: If biological evidences like blood or saliva is contaminated during collection (e.g., by improper handling or exposure to external substances), the results of DNA testing may be unreliable or invalid.  Improper packaging: If evidence is not correctly packaged, it might degrade or be compromised, reducing the accuracy of the forensic analysis. This principle reinforces the need for investigators to handle, package, and store evidence with care to ensure the integrity of the forensic analysis. Proper sampling techniques and attention to detail are critical for producing reliable results. Frye case and Daubert Standard 1. Frye Case (Frye v. United States, 1923)  Background: A man named James Frye was on trial for murder, and his lawyer wanted to use a lie detector test to prove he was telling the truth.   The court had to decide if this new scientific method (the lie detector) could be used as evidence in the trial. The Frye case involved the use of a "systolic blood pressure deception test," an early form of a lie detector test, as evidence in a criminal trial. The court had to decide whether this scientific evidence was admissible.  Ruling: The court established what became known as the "Frye Standard" or "General Acceptance Test." The court ruled that scientific evidence is admissible only if the technique or theory has gained general acceptance in the relevant scientific community.  Key Points: o Focuses on whether the scientific community widely accepts the method or theory. o This standard was used for many years as the main test for determining whether scientific evidence could be admitted in court. 2. The Daubert Standards: Daubert v. Merrell Dow Pharmaceuticals In this case, the court outlined several guidelines to help judges determine whether scientific evidence is trustworthy and valid. Judges are seen as "gatekeepers" and have the responsibility to ensure that the evidence meets these standards before it can be shown to a jury. The Key Factors of the Daubert Standard: 1. Testability: Can the scientific method or theory be tested? Has it been tested in experiments or research? This shows if the idea can be scientifically checked for accuracy. 2. Peer Review and Publication: Has the theory or method been reviewed by other scientists? If it has been published in scientific journals and examined by experts, it is more likely to be reliable. 3. Error Rate: What is the potential for errors in the method or theory? If the error rate is known and controlled, it helps to ensure that the evidence is reliable. 4. Standards and Controls: Are there clear standards for how the scientific method is performed? Consistent procedures help maintain accuracy. 5. General Acceptance: Is the method generally accepted by the wider scientific community? Although this was the focus of the older Frye standard, it remains an important consideration under Daubert.  The Daubert Standard gives judges more flexibility and responsibility than the older Frye Standard, which focused only on whether the method was generally accepted. Under Daubert, judges now look at various factors to ensure that the scientific evidence is both reliable and relevant before it's presented in court.  It provides a more detailed and comprehensive way of evaluating scientific evidence in legal cases, ensuring that what is presented to the jury is based on sound scientific principles.