STUDY MATERIAL AFTER MIDTERM Flashcards
What range in Nanometers is visible to the human eye?
400nm to 700nm is visible light to the human eye
Fluorescence Definition
Fluorescence
* Fluorescence is the emission of light by a
substance which has absorbed light or other
electromagnetic radiation.
* In most cases, the emitted light has a longer
wavelength, and therefore lower energy, than
the absorbed light.
Why Fluorescence?
Fluorescence allows us to:
- enhance friction ridge details
- eliminate backgrounds
- render latent impressions visible
- increase contrast between impression and background
We achieve fluorescence through the application of chemicals or powders and the use of filters.
Two kinds of filters:
Exiter filter
Barrier filter
Common light sources we use for excitation radiation:
- Ultraviolet (UV) light
- Forensic Light Source (FLS) – filtered lamps
AKA - Alternative Light Source (ALS) - LASER
What PPE is required for Chemicals and Alternative Light sources/
Gloves, long sleeves and Eye Protection
Why do we use Ultraviolet (UV) Light
- Search for hair, fibers, bodily fluids
- Use with fluorescent powders
- Use with dye stain – Ardrox
- Reveal bruises
- Enhance details of bite marks
- Reveal untreated fingerprints on
textured surfaces
Other applications:
* Analysis of inks on questioned
documents
* Counterfeiting detection of bank notes
Goggles MUST have an Optical Density factor of OD___ at 532 nm
or better.
OD4
The most useful light to trigger fluorescence at
crime scenes is blue at approx. _____nm
450
What do we search for with Blue Light?
- Hair, fibres, bodily fluids
- Bones, Teeth
- Bloodstains
- Untreated fingerprints on textured surfaces
- Footwear impressions
- Drugs, Paint, Grease
Some examples Powders and Chemicals we use for Non porous and porous surfaces?
- Non-porous surfaces
- Fluorescent powders
- Cyanoacrylate + dye stain
o Ardrox
o Brilliant Yellow
o Rhodamine 6G - Porous surfaces
- DFO (1,8 Diazafluoren-9-one)
- IND-Zn (1,2-indanedione zinc chloride)
Why use chemicals?
- Eliminate background for better contrast
- Improve chances of finding impressions
- Quality of impressions developed with
chemicals is often better than when
developed with powders
Process we do for non-porous
- Cyanoacrylate fuming
- Fluorescent dyes or fingerprint
powders - Vacuum Metal Deposition (VMD)
CA stands for _____________________________
Cyanoacrylate
Porous Chemical Sequence
1A In/Zn
or
1B DFO
2 Ninhydrin
3 VMD
4 Oil Red O
5 Physical Developer
Wet Porous Chemical Sequence
1 VMD
2 Oil Red O
3 Physical Developer
Non-Porous Chemical Sequence
1 CA
2 CA + Dye
3 VMD
Wet Non-Porous Chemical Sequence
Molybdenum Disulphide/ Small particle Reagent
or
VMD
Semi- Porous Chemical Sequence
1 CA
2 Florescent dyes or fingerprint powders
3 VMD
Why do we use filters?
- to apply light of a specific wave length range for excitation radiation
- to see fluorescence
- to photograph fluorescence
What does LASER stand for?
Light
Amplification by
Stimulated
Emission of
Radiation
What are common problems when using chemicals that fluoresce?
- incorrect match of excitation light and chemical
- no barrier filter on camera
- incorrect barrier filter
- insufficient time for eyes to adapt
What part of the matrix reacts to chemicals?
- eccrine sweat
- sebaceous oils
- lipids
- other contaminants
When using chemicals at a scene what are factors to consider?
- history of the substrate: dry, wet, previously wet
- seriousness of the offense
- availability of chemicals/ powders
- value of item
- potential for damage
- substrate
- matrix
- time elapsed between deposition and examination
What should a WHIMIS label include?
- name of product
- pictogram
- signal word
- hazard statement
- precautionary statement
- supplemental label
- name of supplier
What is the best chemical process for processing thermal paper?
- VMD
- acetone and ethanol wash
What part of the matrix does the vmd target?
Fats
Amino acids
Eccrine sweat
What can blue light detect at the morgue?
- bodily fluids
- bloody latent marks
- bite marks and bruising
- unusual marks
What is the nm wave length of a laser?
A single wave length of 532nm
What can a laser be used for?
- search for hairs and fibers
- used as excitation radiation for fluorescence following a chemical application
Through what application do we achieve fluorescence?
- chemicals
- powders
- use of filters
At the start of your video you should start with
a sign on to provide the following information:
Date & Time
. Location
. File number
. Person recording the video
. Other persons present
When taking videos, how long should you wait at the beginning/end of the pan shot before stopping/moving?
5-10 sec
Name two reasons why you would use a dye stain on exhibits treated with CA (cyanoacrylate fuming).
The main two reasons for using dye stains are to enhance the impression and create greater contrast between the fingerprint and the background.
Match the following dye stains that are used with exhibits that have been treated with CA to their recommended viewing FLS wavelength.
505-535 nm
450-485 nm
UV
Ardrox
Brilliant Yellow
Rhodamine 6G
What does ninhydrin react with?
Amino Acids
What is the recommended examination process for wet glass?
Molybdenum disulphide also known as Moly-Di or Small partical reagent (SPR)
For general searching of a crime scene, what is the optimal wavelength of an alternate light source to use?
450nm
What is the recommended dye used to view friction ridge detail developed with CA using the laser?
Rhodamine 6G
T or F
A 360 degree pan should always be completed in one shot.
F
List three considerations when determining how to treat an exhibit with a chemical process.
There are a large number of considerations including: substrate, matrix, type of offence, value, sentimental value, and the portability of the object
A crime scene video should include overall, midrange and close-up shots of an item of interest. The best way to accomplish this is to:
Film the overall shot, pause and then get closer to the point of interest and re-establish the shot at a midrange and continue filming
Place the following processes in the correct order that should be used to develop a fingerprint on a piece of paper.
Ninhydrin
DFO/IN DN
Visual Exam
Oil Red O/ Physical Developer
VMD
Visual Examination - DFO or Indaindione Zinc Chloride, Ninhydrin, VMD, Oil Red O and Physical Developer
T or F
In fluorescence photography, the barrier filter is always placed in front of the light source.
F
Name two reasons why you would use a dye stain on exhibits treated with CA (cyanoacrylate fuming).
Enhance the impression and create greater contrast between the fingerprint and the background.
What to include in the rough sketch?
− Compass direction (North arrow)
− Date & Time sketch was made
− Precise address of the location
− Reference points used
− Who drew rough sketch
− Who took the measurements
− Other pertinent information
What to measure for Indoor scenes?
- Length and width of the rooms
- Thickness of walls
- Thickness and width of doors and direction of swing
- Furniture and anything that could be considered evidence
- Stairways
4 parts of the shoe bottom
Toe, forefoot, arch, heel
3 parts of shoe
Upper, outsole, midsole
Why are hand molds important?
Variations in outsoles made by hand molds
Why is texture important on the bottom of a shoe
It can indicate wear. Texture is valuable when comparing general wear.
2 types of molding
- Compression Molding
- Injection Molding
What is Compression molding?
Waffle maker
What is Siping in shoes or tires?
Thin cuts in outsole to improve traction (boat/deck
shoes). Small slits in undersole instead of 3d ridges
What are the 3 things in footwear that we analyze during the analysis phase?
- Class Characteristics (i.e., level 1 detail)
- General Wear
- Randomly Acquired Characteristics
Possible opinions for footwear comparison conclusion:
- Inconclusive
- Exclusion
- Association of class
characteristics - Higher degree of
association - Identification
Philosophy of Footwear Identification
“Footwear Identification is established by the
agreement of class and accidental
characteristics of such significance or number
that no other logical conclusion can be
reached.”