Forensic Lab Techniques

1.property of a substance that describes how it reacts in the presence of other substances

• chemical properties

• physical properties

• unique properties

• physiological properties

any of several processes used to separate a mixture into its individual components based on their attraction to a stationary liquid or solid

• spectroscopy

• microscopy

• chromatography

• philosophy

test done to establish with certainty the characteristics of a substance

• preliminary test

• presumptive test

• conservatory test

• confirmatory test

properties that can be measured without changing the identity of the evidence

• chemical properties

• physical properties

• unique properties

• physiological properties

allow a field investigator to screen evidence to reduce the number of possibilities and to get a preliminary identification. (saliva, semen, blood, urine, and vaginal secretions)

• confirmatory test

• presumptive test

• preliminary test

• conservatory test

Most widely used microscope

Light source and multiple lenses

Magnifcation between 40x to 1000x

View hair, fibers, and cells

• Comparison microscope

• Stereomicroscope

• Light microscope

• Scanning electron microscope

Sometimes called a dissecting microscope

Light is reflected from the specimen surface

Produces a three-dimensional image useful for dissecting

Better surface details of:

Inspect insect larvae, paint chips, and other small items

• Dissecting scope

• Transmission Electron Microscope

• Comparison Microscope

• Light Microscope

Two microscopes connected to one eyepiece

Two samples are visible side by side

Useful for comparing bullet striations, fibers, and hair

• Stereomicroscope

• Dissecting Microscope

• Light Microscope

• Comparison Microscope

passes electrons through the sample to produce images of internal structures

• Dissecting scope

• Transmission electron microscope

• Scanning electron microscope

• Light microscope

passes electrons over the surface to produce a three-dimensional image

• Comparison microscope

• Transmission electron microscope

• Scanning electron microscope

• Light microscope