Introduction to Forensic Science

Forensic science uses scientific methods to understand events from physical evidence and relevant information, reconstructing legally relevant situations.

Forensic science encompasses various specializations and sub-specializations, including analysis of human bodies, behaviors, materials, substances, digital traces, and artifacts.

Early forensic science involved establishing innocence through evidence like Quintilian's bloody handprint. China developed pathology texts in 1248.

The scientific advancements of the Enlightenment era marked a significant turning point in forensic science development.

Henry Faulds' 1880 paper suggested fingerprints could identify perpetrators, a significant advance.

Bertillon's anthropometry used body measurements and photos to identify suspects—a precursor to biometrics.

Forensic science uses observed data (evidence) to formulate hypotheses about events, unlike other sciences starting with hypotheses.

Forensic science aims to answer questions like who, what, where, when, how, and why by analyzing available information at the scene of an event.

Identifying chemical components in substances like white powder using reference standards.

Extracting a DNA profile and comparing it to reference samples from known individuals to establish identity.

Comparing common features between questioned and known samples to find similarity.

Evidence evaluation based on expert experience, training and judgment.

Evidence evaluation based on observable and measurable data, ignoring personal feelings.

Known samples used for comparison in forensic analysis.

Determining what might be present in a sample, not how much.

Determining the amount or concentration of a substance.

In every interaction, there's a transfer of trace evidence. A criminal's presence leaves behind detectable material.

Physical evidence, including small items like paint chips, fibers, glass, hair, soil, and explosive residue, associated with a crime.

Evidence like tool marks, footwear impressions, and fingerprints analyzed to determine if a feature matches a known sample.

Evidence on digital devices, such as phones and computers, including photos, videos, locations, emails, and texts.

Evidence based on biological components like DNA from blood, saliva, skin cells, and hair.

A meeting to plan the collection and analysis of forensic evidence at a crime scene.

Known samples (e.g., suspect's toolkit, known source of chemical compound) that are used for comparison.

Forensic evidence where analysis is based on established, measurable methods, minimizing personal interpretation. Aims for unbiased results.

Forensic evidence where analysis relies on expert judgment and interpretation, often based on experience and pattern recognition. Requires demonstrably unbiased methods.

Means the evidence's methods are accurate and reliable, with known error rates. It ensures the evidence is scientifically sound.

Means the correct methods were used for the specific evidence and situation. It ensures the evidence is suitable for its purpose.

Unreliable forensic evidence can lead to miscarriages of justice. It undermines the legal system's credibility and fairness.

Lawyers sometimes use scientifically questionable evidence in court to influence a case, leading to inaccurate judgments.

Presenting weak scientific evidence with exaggerated claims, like the Shirley Mcqueen fingerprint inquiry.

Scientific findings aren't always absolute truth. Interpretation and limitations are crucial.

A 2009 report highlighting major weaknesses in forensic science practices, particularly reliability and validation.

Many forensic techniques lack rigorous scientific validation, like handwriting analysis and bitemark analysis.

Many methods rely on human interpretation, leading to inconsistent results between experts.

Experts relying on personal experience ('I've seen this before') instead of research-based conclusions.

The NAS report called for significant reforms, such as establishing a National Institute of Forensic Sciences and standardizing practices.

Another key report examining the validity of forensic feature comparison methods in criminal courts.

The reports emphasize the importance of ensuring scientific validity in forensic techniques used in courts.