Trace Evidence

Trace evidence is evidence that is created when objects come into contact with other objects. This means that when people touch objects with any part of their body evidence can be left behind. It also means that when any object touches another object there is a chance that evidence is left behind. Trace evidence is often small or present in small amounts. Trace evidence includes things like hairs, fibers, fingerprints, DNA, soil, paint, and glass. It can also include marks made by tools or firearms.  In this unit we will learn about several different types of trace evidence and how it is analyzed in the lab.

Since trace evidence is often very small or sometimes even microscopic, it often requires the help of microscopes in order to analyze the evidence in the lab. Before we learn about each type of trace evidence, we will learn about the different types of microscopes used to analyze that evidence. There are several different types of microscopes that are used for different types of evidence.

Introduction

 Microscopes provide a direct image of a small object of interest that often would not be seen by the naked eye. There are numerous types of microscopes. Each type offers the forensic scientist a unique opportunity to view and analyze different types of forensic evidence. Whether the Forensic Scientist is analyzing paint chips or examining for gun shot residue, microscopes make the seemingly ordinary minute evidence come alive in very detailed images. Today, all modern crime labs are equipped with multiple microscopes due to their importance in evidence analysis.

Essential Questions

1. What are the parts of a microscope?
2. Are some types of microscopes better than others for certain types of evidence analysis?
3. When is a microscpectrophotometer used in Forensic Science?
4. Why are microscopes important to Forensic Science?

Module Minute

Microscopes have been used for hundreds of years to make the seemingly invisible, visible. Galileo designed a compound microscope in 1625 that is quite similar in function to compound microscopes that are still widely used today! The "Father of Microscopy", Anthony Leeuwenhoek, made his own microscope lenses to magnify threads that he counted. Among his many contributions to the science of microscopy, he documented bacteria, yeast, blood cells and small water animals with his handmade lenses. Microscopes today are used in Forensic Science to analyze trace evidence that is too small to discern with the naked eye. Microscopes help Forensic Scientists to analyze evidence such as paint chips, items with suspected gunshot residue, glass, soil, blood evidence, tool marks, bullets, illicit drugs, fibers and many other items of evidentiary significance.

Georgia Virtual, Microscopes, CC BY-NC-SA 3.0