Comprehensive Notes on Forensic Science Principles, History, and Admissibility
Definition and Scope of Forensic Science
Forensic science is defined as the application of science to law, encompassing both civil and criminal law.
The application of forensic science must remain strictly accurate and objective.
Forensic science functions as an umbrella term encompassing various professions that utilize specialized skills to assist law enforcement agencies.
The primary professional organization in the field is the American Academy of Forensic Sciences (AAFS), which is the largest forensic science organization and comprises 11 distinct sections.
Key specialized sections and disciplines include:
Criminalistics: The application of scientific methods to recognize, collect, identify, and compare physical evidence generated by criminal or illegal civil activity. It involves the reconstruction of events through the systematic evaluation of physical evidence and crime scene context.
Digital and Multimedia Sciences.
Engineering Science.
Jurisprudence.
Odontology.
Pathology / Biology.
History and Development of Forensic Science
Public awareness of scientific methods in criminal and civil investigations has significantly increased due to prime-time television programs.
The "CSI Effect" has created an unrealistic public expectation that every crime scene will produce definitive forensic evidence.
Forensic science possesses literary roots in the fictional works of Sir Arthur Conan Doyle, whose stories were among the first to incorporate the newly developing principles of serology, fingerprinting, firearm identification, and questioned document examination.
Key historical figures and pioneers include:
Mathieu Orfila: Considered the founder of forensic toxicology.
Alphonse Bertillon: Identified as the founder of criminal identification; developed the anthropometry system of personal identification based on body measurements.
Francis Galton: Conducted the first definitive study of fingerprints and established a systematic methodology for classifying them for filing.
Karl Landsteiner: Discovered that human blood can be categorized into distinct groups.
Leone Lattes: Devised a practical procedure for determining the blood group of a dried bloodstain.
Calvin Goddard: Determined that establishing whether a specific gun has been fired requires matching a bullet with one test-fired from the suspect weapon; introduced the comparison microscope as an essential tool for modern firearms examiners.
Albert S. Osborn: Developed the fundamental principles of document examination and authored the first significant textbook in the discipline.
Walter C. McCrone: Recognized as the world's preeminent microscopist.
Hans Gross: Authored the first treatise detailing the application of scientific disciplines to the field of criminal investigation.
Edmond Locard: Applied Hans Gross's principles within a functional laboratory setting, establishing the world's first crime laboratory in Lyons, France.
Structure and Organization of Crime Laboratories
History and Growth of Crime Laboratories:
In August 1923, August Vollmer established the oldest forensic laboratory in the United States under the Los Angeles Police Department (LAPD).
In 1932, the Federal Bureau of Investigation (FBI) established a national laboratory to offer forensic services to law enforcement agencies across the country. Today, the FBI laboratory is the world's largest forensic lab.
International Crime Laboratory Models:
Great Britain: Operates a national system of regional laboratories organized under the government's Home Office.
Canada: Forensic services are provided through three government-funded entities: three Royal Canadian Mounted Police (RCMP) regional laboratories, the Centre of Forensic Sciences in Toronto, and the Institute of Legal Medicine and Police Sciences in Montreal.
United States Federal Crime Laboratories:
The federal government maintains no single law enforcement agency with unlimited jurisdiction.
Federal forensic services are divided among four major agencies:
The Federal Bureau of Investigation (FBI)
The Drug Enforcement Administration (DEA)
The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF)
The United States Postal Inspection Service
State and Local Crime Laboratories:
State-level laboratories are maintained to serve state and local law enforcement agencies that lack independent access to a laboratory.
Local laboratories serve county and municipal agencies, operating independently of state facilities and funded directly by local government.
Operational Factors:
The organizational structure and specific services offered by individual laboratories depend on local legal requirements, organizational capabilities, parent agency functions, and budgetary or staffing constraints.
Services and Units of Crime Laboratories
Five Basic Services Provided by Full-Service Laboratories:
Physical Science Unit: Applies principles of chemistry, physics, and geology to identify and compare physical evidence.
Biology Unit: Performs identification and DNA profiling of dried bloodstains, body fluids, hair, and botanical materials.
Firearms Unit: Examines firearms, discharged bullets, cartridge cases, shotgun shells, and ammunition components.
Document Examination Unit: Analyzes handwriting, typewriting, paper, ink, and questioned documents.
Photography Unit: Examines and records physical evidence using specialized photographic techniques.
Optional Services Provided by Crime Laboratories:
Toxicology Unit
Latent Fingerprint Unit
Polygraph Unit
Voiceprint Analysis Unit
Crime Scene Investigation Unit
Functions of a Forensic Scientist
Scientific Evidence Analysis:
Forensic scientists must be skilled in applying the principles and techniques of physical and natural sciences to the analysis of physical evidence.
Laboratory analysis represents only half of the forensic scientist's role; the remaining half takes place within the courtroom.
Police investigators rely on three major avenues to solve crimes: confessions, eyewitness accounts, and physical evidence collected from the scene.
Providing Courtroom Testimony:
Forensic analysts may undergo voir dire, a preliminary examination conducted to establish their qualifications, training, experience, and knowledge as an expert witness.
An expert witness is an individual determined by the court to possess knowledge or skills relevant to the trial that will assist the court in establishing the truth.
An expert witness is legally permitted to express an opinion during testimony.
A lay or fact witness can testify only regarding personal knowledge of facts and is prohibited from expressing opinions.
Application of the Scientific Method in Forensic Inquiry
The analysis of physical evidence must strictly adhere to scientific inquiry and the scientific method.
The scientific method acts as a safety net, ensuring investigation outcomes remain untainted by emotion or compromised by distorting, belittling, or ignoring contrary evidence.
It requires seeking answers through the systematic collection, organization, and analysis of facts.
Hypothesis Definition:
A hypothesis represents a specific question to be answered, framed as a tentative and testable statement.
Hypotheses tested over a wide variety of conditions become integrated into scientific theories.
Scientific theories represent the best explanations for natural and physical phenomena and remain subject to continuous testing and retesting.
Steps of the Scientific Method in Evidence Analysis:
Step 1: Formulate a question worthy of investigation.
Step 2: Formulate a reasonable, testable hypothesis.
Step 3: Test the hypothesis through systematic experimentation.
Step 4: Upon thorough validation, the hypothesis becomes suitable as scientific evidence.
Legal Admissibility Standards and Court Precedents
Duces Tecum:
A legal writ commanding a witness to produce specified documents or physical evidence in court.
The Frye Standard:
Originating from Frye v. United States, this guideline establishes that for scientific evidence or procedures to be admissible, the questioned technique, procedure, or principle must be "generally accepted" by a meaningful segment of the relevant scientific community.
Federal Rules of Evidence (FRE):
Provides a flexible standard that does not require "general acceptance" as an absolute prerequisite for admitting scientific evidence.
Governs the admissibility of all evidence, including expert testimony, in federal courts; serves as a model for state evidence codes.
Rule 702 of the FRE dictates that a witness may be qualified as an expert by virtue of knowledge, skill, experience, training, or education.
Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993):
The United States Supreme Court ruled that general acceptance under the Frye standard is not an absolute prerequisite for the admissibility of scientific evidence under Rule 702 of the FRE.
Designated the trial judge to act as a "gatekeeper" responsible for ensuring that scientific evidence is both relevant and reliable.
Established the Daubert Guidelines to assist judges in gauging the validity of scientific evidence:
Has the scientific technique or theory been tested?
Has the technique or theory been subjected to peer review and publication?
What is the technique's potential or known rate of error?
What standards and controls exist to maintain and control the technique's operation?
Has the theory or technique attracted widespread acceptance within a relevant scientific community? (Incorporates the Frye standard).
Kumho Tire Co., Ltd. v. Carmichael:
The Supreme Court unanimously ruled that the trial judge's "gatekeeping" responsibility applies not only to scientific testimony, but to all expert testimony grounded in "technical" or other "specialized knowledge."
Coppolino v. State:
Addressed the legal admissibility of a newly devised scientific drug test.
Demonstrated trial judges' broad flexibility and wide discretion in evaluating scientific inquiry, recognizing the necessity for creating new tests to address novel problems arising in forensic science.
Melendez-Diaz v. Massachusetts (2009):
Addressed the practice of introducing evidence certificates or written laboratory affidavits in place of live courtroom testimony by forensic analysts.
Ruled that introducing forensic evidence via an affidavit or certificate denies the defendant their Constitutional right to cross-examine the forensic analyst.
Specialized Forensic Science Services
Evidence Technicians: Specially trained personnel on 24-hour call to collect and preserve physical evidence at crime scenes.
Forensic Psychiatry: Applies psychiatric principles and medical knowledge to legal matters, competency evaluations, and criminal profiling.
Forensic Odontology: Uses dental identification methods, dental records, and bite mark analysis to assist law enforcement.
Forensic Engineering: Examines structural failures, accident site reconstructions, and mechanical malfunctions.
Forensic Computer and Digital Analysis: Focuses on the extraction, preservation, and analysis of information stored on computer systems and electronic media.