Introduction to Forensic Science and Empirical Methodology
The Nature of Science and Empirical Measurement
Science is defined by its reliance on empirical measurements and characteristics. An empirical characteristic is a property of an object or phenomenon that can be observed and measured in a consistent reality.
Examples of empirical characteristics include:
Density
Mass
Size
Reflectiveness of light
Chemical reactions with other substances
Interactions with other people
The primary goal of using these empirical characteristics is to establish true information about the universe.
In a forensic context, science is used to answer specific factual questions:
How did the crime happen?
When did the crime happen?
Who did the crime happen to?
Where did it happen?
Science is generally focused on the mechanics and facts of an event rather than the "why." The motivation behind a crime is the domain of criminology and psychology. Forensic scientists prioritize physical reality, such as identifying the presence of a specific weapon or injury, over the psychological reasons for the act.
Defining Forensic Science and its Etymology
The word "forensic" is derived from the Latin root forum, referring to a place of debate, such as the Roman forum.
Forensic science, therefore, refers to science as it is applied to a place of debate, which in modern society is the courtroom.
The courtroom involves a debate between two primary sides:
The Defendant: The specific person on trial.
The Prosecuting Attorney: The party whose goal is to prove the defendant committed the crime by presenting evidence.
The Defense: The party arguing against the prosecution's claims.
The Trier of Fact: The judge or jury responsible for deciding which side is correct based on the evidence presented.
There is often a conflict of interest between lawyers and scientists:
Lawyers aim to win the debate and seek certainty to secure a prosecution or a plea.
Scientists must remain objective and honest about the limitations of their observations. They may only be able to provide a percentage of certainty or must acknowledge alternative explanations.
Objective Reality and Evidence Evaluation
Scientific inquiry requires distinguishing between objective facts and subjective opinions.
An objective fact is something measurable and consistent. For example, the number of sesame seeds on a bagel is an objective, measurable characteristic, whereas the degree of someone's "evil" or the size of angels are not scientifically measurable.
Physical evidence (as opposed to testimony) includes items like:
Footprints
Body fluids
Hair
Fibers
DNA
Bones
The role of the forensic scientist is to turn raw physical evidence into useful information for the case. This involves making empirical observations and then interpreting their meaning.
Example: In DNA analysis, the empirical observation is often the length of a specific chunk of DNA. The interpretation is what that length implies about the identity or source of the sample.
Assessing the Validity of Scientific Claims
When evaluating claims (such as those found on social media or in a courtroom), it is necessary to distinguish between those who are correct, wrong, lying, or bullshitting:
Wrong: Someone who believes they are correct but is factually mistaken.
Lying: Someone who knows they are incorrect but intentionally presents false information.
Bullshitting: Someone who presents information without regard for its truth. They may believe they are right but are unwilling to admit they could be wrong or lack the data to back up their claims.
Methods for determining the quality of science include:
Qualifications/Credentials: Evaluating if the person making the claim has the appropriate training or background in that specific field.
Previous Knowledge and Logic: Comparing the claim against established scientific laws and logic.
Testing the Relationship: Actively testing the statement through experimentation. For example, testing if a vitamin improves skin by comparing "before" and "after" photos of a test group.
Specificity: Good scientific claims should be specific rather than broad or vague.
The Scientific Method in Forensic Practice
Forensic science operates both in the lab and at the crime scene. These two areas must work in tandem.
The process involves:
Making observations: Identifying patterns at a crime scene (e.g., shoe prints).
Developing a general theory: Proposing that certain types of evidence (like shoes) can leave unique marks.
Forming a hypothesis: A specific, testable prediction (e.g., "This specific shoe made this specific print").
Testing the hypothesis: Comparing the evidence (the print) with the suspect's shoe.
Stating a conclusion: Determining if the evidence supports or disproves the hypothesis.
In shoe print comparison, scientists look at shape, size, and wear patterns (accidental damage to the shoe that creates unique marks). If a print matches the shape and size but lacks the specific wear patterns of a suspect's shoe, the conclusion should reflect that the print was likely not made by that shoe.
The Principle of Falsifiability
Falsifiability is a cornerstone of good science. It means that a hypothesis or test must be constructed in a way that it can be proven wrong by empirical observations.
Falsifiable hypotheses are practical because they can be disproved easily and do not require an infinite number of observations to be validated.
Examples of Falsifiability:
Hypothesis: "Chicken eggs are white."
Test: Finding a brown egg disproves the hypothesis. Therefore, the statement was falsifiable.
Hypothesis: "Human blood turns green when exposed to leucomalakite green."
Test: If the blood turns any other color, the hypothesis is disproven. (Note: The species-specificity of this test would require further phrasing to be fully accurate).
The Concept of Uniqueness: The claim that an object (like a fingerprint) is unique is technically not a falsifiable hypothesis. To disprove uniqueness, one would have to compare an object against every other similar object in the universe, requiring an infinite number of observations. While uniqueness is a generally accepted theory, it is difficult to validate under strict falsifiability models.
Professional Paths and Education in Forensic Science
There are different models for how forensic experts are trained:
The Experience Model: Traditionally, police officers with significant field experience testified about crime. However, they often lacked the scientific background to explain the "why" or the underlying physics/chemistry/biology of the evidence.
The Civilian Scientific Model: This is the modern ideal. It involves individuals with formal scientific education in fundamental sciences who then receive specific training in the police/forensic applications of those sciences.
Accreditation: FEPAC is the accrediting body for forensic science education programs. Formal education ensures a standard of knowledge regarding empirical observations and their validity in court.
Continuing Education: Professional organizations are vital for maintaining and expanding a forensic scientist's expertise throughout their career.
Questions & Discussion
Scenario: Blood Alcohol Concentration (BAC)
Context: A medical research standard indicates a BAC of is generally lethal. A woman is found dead with a measured BAC of . There were beer cans and a bottle of vodka at the scene.
Question: As a scientist in court, what are you willing to back?
Response Analysis:
The most useful and scientifically defensible answer is that she almost certainly died from alcohol poisoning, though one should leave room for minimal doubt (the "Strong/Assertive" approach).
Saying "I don't know" or that a conclusion cannot be reached is accurate but not useful to the trier of fact given the high degree of scientific correlation between BAC and death.
Poll: Objective vs. Subjective
Question: Which of the following is an objective, measurable characteristic: the number of sesame seeds on a bagel, the size of angels, or how evil a person is?
Answer: The number of sesame seeds on a bagel is the correct answer because it is an objective measurement in a consistent reality.