Introduction

Forensic science also known as criminalistics is the application of science in criminal and civil laws. It is the intersection of law and science.

The science used in legal investigations includes but is not limited to: chemistry, biology, physics, computer science, medicine, pharmacology, anthropology, archaeology, marine science and psychology.

The media has increased the public’s awareness of the use of science in criminal investigations. It has created unrealistic expectations such as:

• the amount of time a procedure takes
• every crime scene yields forensic evidence that supports a case (myth)

The CSI Effect is the unrealistic and detrimental expectations that a prosecutor’s case should be bolstered by forensic evidence. This has led to juries placing lots of weight on forensic evidence.

History of Forensic Science

Key People

The mid 19^th century is when forensic science began to coalesce as a recognized principle. The key people included:

Victor Balthazard

• Medical examiner in Paris
• Helped advance fingerprint, firearm and hair analysis
• Probability models for fingerprints (1 / 10⁶⁰ chance for shared fingerprint)
• Photographic method for comparing bullet markings
  • Firing pin and fabric impressions of a soft lead bullet moving through fabrics
• Wrote the first comprhensive book on hair analysis entitles - The Hair of Man and Animals (1910)

Alphonse Bertillon

• Developed the first systematic method fo the identification and suspects of criminals
• Called Anthropometry or Bertillonage
  • Based on 11 body measurements
  • Descriptive information
  • Photographs
  • Fingerprints (not commonly collected)
• Commonly used from 1883 to early 1900s
• Despite initial resistance to fingerprint use, Bertillion was the first person to use them to solve a crime

Sir Francis Galton

• Fist classification system for fingerprints
  • Basic patterns: Loop, Arch and Whorl
• Published Finger Prints (1892) which brought fingerprinting to the forefront of criminal identification
  • Still considered the primary reference in the field

Edmond Locard

• Trained both law and medicine
• Established a Forensic laboratory in Lyon, France
• Interested in microscopic and trace evidence
  • Believed that it was crucial in linking people to places
• Most famous for Locard’s Exchange Principle
  • Usually paraphrased as ‘every contact leaves a trace’

Science and the Law Today

Law: A Way to Settle Disputes

The law is a way disputes can be settled:

• Criminal Law: between individuals and the state
• Civil Law: among individuals or entities

Guided by the law, precedent and functions using and adversarial system:

• Two opposing sides arguing for acceptance
• The finder or trier of fact usually a judge or jury determines the truth based on evidence presented by two opposing sides (outcome based)

Science: A Way to Study the Natural World

Science enables us to ask basic questions (ex. what was the cause of death) and helps us answer these questions using observation, testing and interpretation through logic (scientific method).

Scientific Definitions

Hypothesis

A testable idea, not simply an educated guess; the tenative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation

Scientific theory

Explanation (not guess) of some aspect of the natural world that has been substantiated through repeated experiments or testing. Can be supported, rejected, or modified based on new evidence

Fact

1. A confirmed or agreed-upon empirical observation or conclusion
2. Knowledge or information based on real occurrences

The core logic of science is to test ideas with evidence. The scientific method offers a framework for how to conduct research. Science is iterative (not linear and not predetermined) and circles back so that useful ideas are built upon; the framework includes:

• Asking questions
• Making observations
• Formulating hypotheses
• Performing experiments
• Collecting data
• Drawing conclusions

Science is collaborative and depends on interactions within the scientific community. Different parts of the process may be carried out by different people at different times.

Science relies on creativity as it is exciting, dynamic and unpredictable. Science relies on creative people thinking outside the box. Good problem soliving and solid methodology is important for both “hard” and “soft” sciences.

Science is never over, and scientific conclusions are always revisable if warranted by the evidence.

• Science is falsifiable
• Something cannot be scientific if it does not admit the possibility of being shown false

Most scientists would not say that science leads to an understanding of the “truth”.

• Science is a determination of what is most likely to be correct at the current time with the available evidence

The Role of the Forensic Scientist

A forensic scientist is not concerned with the truth. A forensic scientist only cares about the evidence:

• Proper evidence collection
• Identifying the evidence
• Contamination issues
• Proper documentation
• Clear communication of ideas

Modern Practice of Forensic Science

• Training includes a variety of forms; CSI (police officers, general patrol…) and for Forensic Scientists (scientists / technicians, undergraduate education…)
• Public laboratories - funded by the government
• Private laboratories - designed to make a profit
• Forensic scientists can use science from several areas including biology, chemistry, toxicology, documents, firearms, toolmarks and electronics
• Academic professors teach forensic science, create mock crime scenes, curriculum development, and research

Types of Legal Proceedings

Legal Proceedings

Criminal Cases - Government and Individual

Violation of criminal laws (felony / misdemeanor)

Guilty beyond a reasonable doubt (99%)

Civil Cases - Individuals

Lawsuit or being sued (ex. patent infringement)

Preponderance of evidence (51%)

Jurisdictions

Different legal rules and procedures (local, state, federal, etc.)

Legal Proceedings: Roles

• Trier / Finder-of-fact
• Prosecution / Plaintiff
  • Prosecution: Bears the burden of proving a defendant guilty beyond reasonable doubt
  • Plaintiff: Prove case by preponderance of the evidence
• Defendant
• Forensic scientists can testify on either side

Forensic Scientist’s Day in Court

• Analysis → Report → Subpoena
• Voir Dire
  • Background, training, experience
• Direct Examination
  • Lay foundation for the admissibility of the evidence in question
• Cross Examination
  • Discredit witness or evidence
• Re-direct / Re-cross

Ethics and Forensic Science

• No one code of ethics
  • Ex. The American Academy of Forensic Sciences
• In general:
  • Do the best work you can do on every case that is submitted
  • Provide a complete and honest report of your work
  • Testify using their scientific opinion based on the report and their knowledge in the field
• It is possible to have situations where different experts may draw different conclusions from the same evidence
  • Difference of opinion ≠ Unethical
  • Present and defend; the trier of fact makes the ultimate decision

Quiz