Diverse Examples of Trace Evidence Analysis Lab Reports

Introduction

Trace evidence analysis is a critical aspect of forensic science, involving the examination of small materials that can link a suspect to a crime scene. This evidence can include fibers, hair, glass, paint, and more. Forensic scientists conduct systematic analyses to establish connections and provide insights into criminal investigations. Below are three diverse examples of trace evidence analysis lab reports that illustrate different applications in the field.

Example 1: Fiber Analysis from a Crime Scene

In this case, forensic scientists were tasked with analyzing fibers collected from the victim’s clothing and a suspect’s jacket. The purpose of the analysis was to determine whether the fibers from the suspect’s jacket matched those found on the victim, potentially linking the suspect to the crime.

The lab report details the following procedures:

Sample Collection: Fibers were collected using tape lifts from both the victim’s clothing and the suspect’s jacket.
Microscopic Examination: A comparison microscope was used to observe the color, diameter, and cross-sectional shape of the fibers.
Chemical Analysis: Fourier Transform Infrared Spectroscopy (FTIR) was utilized to determine the chemical composition of the fibers.

Results: The analysis revealed that the fibers from the suspect’s jacket matched the characteristics of the fibers found on the victim. The FTIR analysis confirmed that both samples contained the same chemical composition, suggesting a strong likelihood of transfer during the crime.

Notes: Variations in fiber color or composition could indicate different sources or environmental exposure. Additionally, further analysis could include dye analysis or comparison with a database of known fibers.

Example 2: Hair Comparison in a Burglary Case

In this instance, trace evidence analysis focused on hair samples found at the crime scene of a burglary. The objective was to establish whether the hair collected could be linked to the suspect apprehended nearby.

The lab report outlines the following steps:

Sample Collection: Hair samples were collected from the crime scene and from the suspect’s vehicle.
Microscopic Examination: A comparison was made using a microscope to evaluate medullary patterns and cuticle structure.
DNA Analysis: Nuclear DNA analysis was performed on the hair root, if available, to provide a definitive match.

Results: The microscopic examination showed similarities in the hair characteristics between the crime scene samples and those from the suspect’s vehicle. The DNA analysis confirmed that the hair matched the suspect, providing conclusive evidence linking them to the crime.

Notes: It’s important to note that hair comparisons can be subjective, and DNA analysis is crucial for providing definitive evidence. Future reports could explore mitochondrial DNA analysis when nuclear DNA is not available.

Example 3: Glass Fragment Analysis in Hit-and-Run Incident

This example involves the analysis of glass fragments collected from the scene of a hit-and-run accident. The goal was to determine the type and source of the glass to identify the vehicle involved in the incident.

The lab report includes the following methodologies:

Sample Collection: Glass fragments were collected from the pavement at the accident site and a nearby vehicle suspected of involvement.
Physical Comparison: The size and shape of the glass fragments were documented, and density measurements were taken using a liquid displacement method.
Refractive Index Analysis: The refractive index of both samples was measured using a GRIM-3 refractometer to compare the glass characteristics.

Results: The analysis indicated that the glass fragments from the accident scene and the suspected vehicle had matching physical and optical properties. This suggests that the vehicle was likely the source of the glass found at the scene.

Notes: Variations in glass composition can be influenced by the manufacturing process or environmental factors. Further analysis could include elemental analysis to compare trace elements within the glass samples.