Forensic Evidence EEvidence: ,Admissibility, and the Role of Experts

In practice, evidence is used to try connecting two things together: a suspect with a crime scene, a weapon to a wound, a computer message with a criminal act, or a poison to a cause of death.
Most often we deal with various types of material evidence; physical items serve in this key linking role.
Forensic evidence spans broader categories beyond physical items, including chemical, biological, cyber, linguistic, and behavioral evidence.

Ideally, the link between the item of evidence and its source should be unambiguous, linking one person from among all others with one unique crime scene to the exclusion of all other possibilities, though the certainty of the level of connection may not be possible.
Locard's principle: when two objects come into contact, there is a transfer of material.
We need to discover a way to find, collect, and analyze this transferred material to establish a bridge between the two objects.
However, the term “evidence” is deceptive: at the crime scene, there are no labels indicating relevance, and evidence is often lost among environmental items with no bearing on the case.
Finding the important and relevant evidence may be like finding the proverbial needle in a haystack; the key ingredient is recognizing relevance.

Entertainment often exaggerates the speed and certainty of solving cases; in real life, crime scene investigations require hard work, skill, experience, and insight.
The investigation relies on the ability to observe and perceive important information from among many pieces of evidence.
Fingerprint experts, photographers, firearm analysts, and many other specialists contribute their refined skills.
Each expert provides insights into what the evidence can provide to the investigation.
The majority of this course is devoted to showing the value that scientific disciplines and their practitioners can bring to criminal investigations.
At the heart of forensic evidence is the value it can tell the trier of fact—the court.

If evidence cannot inform the trier of fact, it is legally useless and typically inadmissible.
Evidence must be more probative than prejudicial: forensic evidence should probe the question at hand and provide unbiased information without unfairly prejudicing or confusing the court.
These factors determine the value of forensic evidence in court proceedings.
Evidence may be anything introduced as part of a trial and may take many forms.

Physical evidence is generally recognized as a material object (e.g., a weapon, a fingerprint, or an item of clothing) that can be observed and measured.
It forms part of the broader world of evidence, which encompasses many types of forensic evidence including chemical, biological, cyber, linguistic, and behavioral evidence.
In successive major sections of this book/course, we will focus on each type of evidence in turn.
Evidence typically provides two key types of identification or comparison analysis, which we will examine in the next video.

The ability to recognize relevant evidence has practical implications for investigation quality and outcomes.
Ethical considerations include avoiding overinterpretation, ensuring fairness to the defendant, and maintaining objectivity in analysis.
The multidisciplinary nature of forensic science means collaboration among experts is essential to construct a coherent and credible narrative for the court.

The material covered lays the groundwork for understanding how crime scene investigations integrate diverse scientific disciplines to evaluate and present evidence.
The next section/video will delve into the two key identification or comparison analyses mentioned above and apply them to real-world scenarios.