Forensic Science: Trace Evidence and Microscopy Comprehensive Study Guide (copy)

Trace Evidence

Any small, minute physical material transferred between people, objects, or a crime scene during the commission of a crime.

Locard's Exchange Principle

Every contact leaves a trace; it defines the principle of cross-transfer between interacting physical entities.

Primary Transfer

Direct transfer of material from one source to another without an intermediary.

Secondary Transfer

Transfer occurring via an intermediate surface or entity.

Persistence

How long transferred evidence lasts on a surface after being transferred.

Microscopy

The use of microscopes to examine small objects and details.

Total Magnification Formula

Total Magnification = Ocular Lens Magnification × Objective Lens Magnification.

Resolution

The minimum distance required between two separate objects such that they can still be distinguished as two distinct objects.

Comparison Microscope

Consists of two compound microscopes joined by an optical bridge allowing two specimens to be viewed side-by-side.

Ocular Calibration Factor (OCF)

A formula to improve measurement accuracy, calculated by OCF = (SSD × K) / ASD.

Contamination

Any transfer of material that takes place after activity surrounding the crime has ceased.

Depth of Field

The range of distance within which objects are in focus at a given magnification.

Field of View (F.O.V.)

The total physical area visible when looking through the eyepiece of a microscope.