Forensic Microscopy Get ready for some short notes

Forensic Microscopy • Generally takes one of six forms depending on the type of

Compound Microscopes • • The “classic” microscope Light is passed through object from beneath

Compound Microscopes • Major Components – Eyepiece – Tube – Nosepiece – Objectives –

Comparison Microscopes • Essentially two compound or stereographic microscopes joined by a “bridge” •

Stereographic Microscopes • Most frequently used type of microscope in forensics • Light is

Polarizing Microscopes • A special microscope application that outfits a “normal” microscope with two

Polarizing Microscopes Polarizing microscope view a a thin slice of granite Blemish on an

Microspectrophotometer • A beam of light is aimed at the object and its spectrum

Electron Microscope • Unique in that it uses a beam of electrons aimed at

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Forensic Microscopy Get ready for some short notes! • Ch. 7 Quiz on Monday • HW due Mon: Ch. 7 foldable and supplemental ? s • If you were absent yesterday you MUST make up your exam during 8 th or after school TODAY!

Forensic Microscopy • Generally takes one of six forms depending on the type of evidence to be examined • Light microscopes: – Compound microscope – Stereoscopic microscope – Comparison microscope – Polarizing microscope – Microspectrophotometer • Electron microscopes – SEM – scanning e- microscope

Compound Microscopes • • The “classic” microscope Light is passed through object from beneath Image is upside down and backwards May possess a zoom magnification or multiple lenses of varying strength • Monocular and binocular versions • Generally up to 1000 x magnification • Higher magnification limitations – “Depth of focus” is decreased and creates focusing challenge – Cuts down on available light

Compound Microscopes • Major Components – Eyepiece – Tube – Nosepiece – Objectives – Stage – Focus – Arm – Base

Compound Microscopes

Comparison Microscopes • Essentially two compound or stereographic microscopes joined by a “bridge” • Vital for side by side comparison of two pieces of evidence • View can show either microscope or can be “split” to show both at the same time • Especially useful in ballistics and hair/fiber cases

Comparison Microscopes

Stereographic Microscopes • Most frequently used type of microscope in forensics • Light is passed either through an object or from above • Image is projected right side up and correct right to left • Usually the only method for opaque forms of evidence • Especially useful for soil analysis, entomology and macroscopic evidence • Magnification generally ranges from 2 x to 125 x • Often called “dissecting” microscopes

Stereographic Microscopes

Polarizing Microscopes • A special microscope application that outfits a “normal” microscope with two devices (a polarizer and an analyzer) • The polarizer is used to impact incoming light waves to reveal special properties of a material • Affected light waves then pass through analyzer before hitting the eye • Especially useful in soil analysis (minerals) and the identification of artificial fibers

Polarizing Microscopes

Polarizing Microscopes Polarizing microscope view a a thin slice of granite Blemish on an LCD screen visible in polarized light (right) but not in normal visible light (left)

Microspectrophotometer • A beam of light is aimed at the object and its spectrum can be collected • The specific spectrum will be unique to particular chemicals, fibers, etc. • Spectral “fingerprints” can then be used to determine specific matches between different evidence samples

Microspectrophotometer

Electron Microscope • Unique in that it uses a beam of electrons aimed at the object – Does not use light • Extremely high magnification possible – Ranging from 10 x – 100, 000 x • Can also be used as a spectroscope in some applications • Useful in gunshot residue cases • Very expensive

Electron Microscope

Electron microscope