Forensics Test

What is the chemical name for Alcohol?

Ethanol or ethyl alcohol

what is the chemical formula for ethanol

CH3CH2OH

What process produces alcohol?

fermentation

what does fermentation use for fuel?

plant sugars or carbohydrates

how much beer is considered one drink?

12oz

how much 80 proof alcohol is considered one drink

1.5oz

what does ABV stand for?

alcohol by volume

what does BAC stand for?

blood alcohol content

what is the percentage of alcohol for a 120 proof liquor

60% (proof is 2x the ABV)

what is the role of a toxicologist?

1. responsible for identifying drug overdoses

2. administering blood tests and analyzing the blood samples for poisons

3. analyzing urine for illicit drugs (not alcohol)

what is the most heavily used legal drug in the US?

alcohol

what two organs absorb alcohol into our bodies?

stomach (>20%) and small intestine

what are some factors that affects how well alcohol is absorbed?

1. the time taken to consume drink(s)

2. alcohol content of the beverages consumed

3. amount of alcohol consumed

4. quantity and type of food that may be present in your stomach at the time of consumption

true or false: urine can be used by a toxicologist if no blood is available

false - urine alcohol tests can be very inaccurate

what is the relationship between alveolar breath and the amount of alcohol in someone’s blood?

the amount of alcohol found in 2100mL of breath is equivalent to the amount of alcohol in 1mL of blood

in the 1960’s what was the legal BAC limit for driving? what is it now?

.in the 1960’s it was 0.15%, it is now 0.08%

what is the legal BAC for a commercial bus driver in the US?

0.04%

what does the Reinsch test detect? what is it unable to detect?

it detects heavy metals in body fluids and tissues. it is not able to detect copper metal, because it uses a copper strip during the test.

why is carbon monoxide bad for the body

it is capable of binding to the hemoglobin in red blood cells faster than an oxygen molecule. if carbon monoxide is present in a high enough level, it will block the body from obtaining the oxygen needed and the individual will asphyxiate.

how long does it take for alcohol to be completely absorbed in the body?

it takes 30-90 minutes after the final drink

how long does it take for the alcohol concentration in the blood to peak?

it will peak 2-3 hours after the final drink

what is the most effective analytical technique for detecting unknown drugs/toxins in the body?

GC/MS machines

what is not apart of the mechanical system of a compound microscope: coarse adjustment, objective lens, body tube, stage?

objective lens

Which microscope is the most frequently used and versatile microscope found in the crime laboratory?

the stereoscopic microscope

The major attractions of the scanning electron microscope (SEM) include all of the following except: its high magnification, the ability to polarize light, its high resolution, its great depth focus

its ability to polarize light

Which microscope can be used to determine whether a suspect has recently fired a gun?

a scanning electron microscope

the ‘fingerprint’ IR spectrum can be seen using a…

microspectrophotometer

True or False: The mechanical system of a microscope is composed of six parts

true

True or False: The magnification of a microscope with a 10x eyepiece and a 10x objective will be 1,000x

false

True or False: The polarizing microscope is best used for forensic microscopy requiring a side-by-side comparison

false

True or False: The stereoscopic microscope is the most frequently used and versatile microscope found in the crime laboratory.

true

True or False: With the development of the scanning electron microscope, a forensic analyst can now view a particle under a microscope while, at the same time, a beam of light is directed at the particle in order to obtain its absorption spectrum. 

false

Name two types of images and explain the difference between them

 virtual (what you see through a magnifying glass or compound microscope) and real (what you see when something is projected or through stereoscopic)

List and define the two types of lenses in an ordinary microscope

ocular (eyepiece) and objective

Name two types of illumination and explain the difference between them. What types of specimens are viewed under each type of illumination?

transmitted-translucent, vertical/reflected - opaque

What is a condenser? Name and describe the simplest type of condenser

collects and concentrates light, diaphragm

Define parfocal

maintains focus when switching between objective lenses

What is the difference between a monocular and a binocular microscope?

monocular - one eyepiece, binocular - two eyepieces

How does one determine the total magnification of a compound microscope?

eyepiece (ocular) times objective

What does numerical aperture describe?

ability of a lens to resolve detail into separate images. the higher the number, the greater the resolution

What is the maximum useful magnification for a compound microscope? Why?

1000 times, any more magnification would not provide any more detail (empty magnification)

What happens to a compound microscope’s field of view when you increase its magnification? How does this affect the way a microscopist views specimens under a compound microscope?

decreases, must keep what you are looking at centered

What is a comparison microscope? How is the image viewed through a comparison microscope different from one viewed through an ordinary or compound microscope?

allows you to compare two specimens for similarities. the view is split into two fields, each containing one of the specimens

When using a comparison microscope, why is it important to closely match the optical characteristic of the objective lenses?

both specimens set at equal magnification for better comparison

What is the most frequently used and versatile microscope found in the crime laboratory? List three reasons why this type of microscope is so widely used.

Stereoscopic - great depth of focus, wide field of view, large working distance (big bulky specimens)

What is plane-polarized light?

light confined to a single plane of vibration

Name two types of physical evidence that are often characterized using a polarizing microscope.

birefringent minerals in soil and synthetic fibers

What is a microspectrophotometer? What advantage does it enjoy over the spectrophotometer for analyzing physical evidence?

microscope connected to spectrophotometer via computer. Specs alone are not well-suited for small particles

Briefly explain how a scanning electron microscope (SEM) produces an image.

a beam of electrons focused by electromagnets is aimed at specimen and the electron emissions are viewed on a cathode ray tube

What device can be coupled to an SEM to produce a picture of the elemental distribution of a specimen? Briefly describe how this combination of devices can be used to determine whether a suspect has recently fired a gun.

X-ray analyzer sorts the x-rays according to their energy values and those can be compared to known element energy values. Firing a gun leaves trace elements on the hand that fired it, tape is used to lift residue, then the tape is hit with electrons to determine size, shape, and element composition of the particles

Examining two bullets to see if the same gun fired them.

comparison

Determining the chemical composition of paint chips.

microspectrophotometer

Identifying birefringent minerals present in soil.

polarizing 

Examining a large specimen, such as a tool or piece of clothing.

stereoscopic

Examining extremely tiny specimens that require very high magnification.

SEM