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Microscope and Fibers Lecture Notes

Microscope

· Parts and Uses - use diagram (refer to appendix)
· Care and Maintenance

o How to carry a microscope
o How to clean a microscope
o How to store a microscope

· How to Focus?

Visually line the slide up with the lens.
Focus on low power.
Move slide so object is in the center of the field of vision.
Refocus on medium power using fine adjustment.
Again, make sure the object is in the center of the field of vision.
Refocus on high power using fine adjustment ONLY!

Fibers

· Fibers are commonly found with burglary, assault, breaking and entering, hit and run accidents, etc.
· Fibers can come from clothes, carpet, curtains, wigs, furniture, etc.
· Natural Fibers - produced entirely from plants or animals

Animal fibers

Sheep - wool
Goats - mohair & cashmere
Camels
Llamas
Rabbit
Mink

Plant fibers - cotton

· Man-Made Fibers

Regenerated Fibers - produced using natural raw materials ( ex. - rayon)
Synthetic Fibers - produced using synthetic chemicals (ex. - nylon & polyester)

· Identification Using Fibers

"Fit together" like puzzle pieces when fabric is torn - conclusive evidence
Microscopic comparison - color, diameter, striations
Color comparison of specific dyes used with micro-spectrophotometer or chromatography
Chemical composition - make sure fibers are from the same generic class and subclass (if possible) with infrared spectrophotometry

· Collecting and Handling Fibers

Clothes are placed in paper bags with each article going into a separate bag.
Carpets and bedding should be folded and placed in a paper bag to protect the areas that may contain fibers.
Fibers may be removed form an object by using clean tweezers and a folded piece of paper that is labeled with the location of the sample, date, time, and name of investigator.
Most objects will be examined in the lab to find fiber evidence; fibers are usually not examined at the crime scene.