Unit IV Guided Notes: Document Analysis &
BallisticsName:__________________________
What sort of cases involve questioned documents?
A questioned document is
____________________________________________________________________________
___________________________________________________________________.
These investigations include:
· Trying to determine the source of a threat or note
· Identifying forgeries and counterfeits
· Identifying alterations made to documents
Paper Comparison
Investigators may try to compare the paper of a questioned
document with that of an ____________________ (sample from known
source).
Investigators will compare:
___________________________ occurs when the electrons of a
material absorb short-wave energy (i.e. UV light) and immediately
emit longer wave energy (i.e. visible light). Occurs because the
electrons become excited then almost immediately return to lower
energy orbitals.
· Material paper is made from
· Density
· Thickness
· Dyes / bleaches
_______________________________ are near-transparent designs
added to papers, often for the purpose of making the paper harder
to forge. The mark can be seen by holding the paper up to the
light. The design is made by _____________________________________
in certain areas.
· Fluorescence under UV light
· Watermark
Ink Comparison
Investigators may try to compare the ink of a
_____________________________________ with that of an
___________________________(sample from known source).
Alternatively, ink may be analyzed to show that a document has
been altered or back-dated.
How might ink analysis show that a document has been
altered?
How might ink analysis show that a document has been
back-dated?
The main technique used to identify / compare inks is
____________________________________________________.
First, however, the ink has to be ________________________ from
the questioned document.
1. Samples of the questioned ink are collected by punching out
‘_____________________’ with a hypodermic needle
2. The microdots are put in a small vial with
_________________________to separate the ink from the paper. The
ink/solvent mix can then be analyzed using thin layer
chromatography.
Thin layer chromatography is a method used to separate
components of a mixture.
· In thin layer chromatography, a sample is placed near the
bottom of a plate (the _____________________________). Usually, the
plate is made of ____________________________________
________________________________________________________________________________________.
· The plate is placed within a small chamber containing a small
amount of liquid solvent (the _______________________). The sample
should be just above the solvent.
· The solvent (mobile phase) moves up the plate (stationary
phase) by ___________________________________.
·
____________________________________________________________________________________________
____________________________________________________ depending on
their relative affinity for the solvent vs the plate. (i.e. the
more they are attracted to the solvent the faster/farther the
molecule will climb up the plate.)
· The _________________________________________of each component
in the mixture can be calculated and compared to an exemplar or to
a database maintained by the Secret Service & IRS
Calculating Rf Values
Counterfeiting and Money Security
US money has a number of features designed to make
counterfeiting more difficult. These include:
· Use of subtle colors that are difficult to duplicate
Did you know?
The US Secret Service was founded in 1865 to combat
counterfeiting. Historians estimate that up to 1/3 of all money in
circulation at that time was counterfeit.
Even today, the USSS confiscates about $80 million in phony
money each year.
· Large, vivid portrait that stands out from background
· Portrait watermark bills greater than $4
· Two ‘5’ watermarks on $5 bills
· Color changing ink (green – copper) on number for all
bills
· Color changing ink (green – copper) on bell for $100
· 3D security ribbons
· Raised printing
Alterations, Erasures, and Obliterations
Investigators may also need to examine whether a document has
altered from the original.
An
______________________________________________________________________________________.
· Can be detected with a microscope
· Sometimes the original ink my still be detected using UV or
infrared light
An ___________________________________________ is when writing
has been purposefully made unreadable by
_____________________________________________________________.
· If both inks used are the same, its nearly impossible to tell
what the first markings were.
· If different inks were used, infrared photography may reveal
the first ink
Handwriting Analysis
When people are writing naturally (without attempt to disguise
their writing or copy someone else’s), handwriting is thought to be
unique.
Handwriting can vary in:
· Letter shape / overall style
· Line quality (shaky, smooth, wavering, rhythmic, etc)
· Spacing of words and letters
· Size of letters
· Pen lifts
· Connecting strokes
· Beginning & ending strokes
· Pen pressure & differences between up and down pen
pressure
· Slant
· Baseline (straight, move upward or downward, above or below
line0
· Placement of _______________________ (crossing of t’s and
dotting of I’s and j’s)
Deliberately disguised handwriting is more difficult to
correctly identify, but most people find it difficult to disguise
handwriting for long periods of time.
In order to obtain good writing exemplars detectives will do the
following:
· Use samples that are longer than a page
· Dictate the writing at least 3 times (disguised writing will
show more natural variation than normal writing
· Use the same phrases and words that are in the questioned
document
· Instruct that the person not only write in capitals or only in
lower case
· Combine signatures with regular writing
Ballistic Analysis Guided NotesName:_______________________
Types of Firearms
________________________ are designed to be held and fired with
one hand.
· ___________________________ can only fire one shot before
being manually reloaded.
· A ____________________________ contains several cartridges in
a revolving cylinder. When one shot is fired, the cylinder rotates
so that the next cartridge is in place to be fired.
_______________________________________________.
· A _______________________________________________ contains a
magazine with several cartridges; as one bullet is fired the next
cartridge is loaded.
· An ___________________________________ (e.g. machine gun) will
continue to fire bullets as long as the trigger is held down
(________________________________________________________).
Did you know?
A _____________ is what is fired (the projectile that exits the
barrel of the firearm). A ______________ contains the bullet plus a
casing, primer, and propellant.
_____________________________ are fired while resting on the
shoulder.
· _________________________ have cartridges and bullets similar
to handguns.
· ____________________________ ammunition is called a
__________________ and contains numerous ball-shaped projectiles
called ____________.
Like handguns, rifles and shot guns may be single shot,
semi-automatic, or automatic.
Bullet Comparisons
When a bullet is fired from a gun, the inner surface of the gun
barrel leaves markings along the bullet that allow investigators
to:
· match a bullet to a particular type of gun (by examining class
characteristics against a database)
-or-
· match a bullet to a specific gun (by comparing individualized
characteristics of the evidence bullet and a test bullet fired from
a confiscated gun).
Why do guns leave marks on bullets?
· The interior (______________) of gun barrels are
_____________________(impressed with spiral
_________________________) in order to make the bullet spin as it
is fired – this ensures that the bullet does not tumble end over
end but instead follows a smooth and accurate course.
· The spaces between the grooves within the bore are called
_____________________.
· The bore diameter (from land to land) is the
___________________ of the gun.
Class characteristics
The lands and groves of the gun bore leave a negative impression
on the bullet (called _____________________________) that can help
identify the type of gun a bullet was fired from.
Specifically, investigators will examine
·
______________________________________________________________________
·
______________________________________________________________________
Class characteristics of known weapons are maintained in an FBI
record called the General Rifling Characteristics File.
Individualized characteristics
Imperfections in the gun bore produce very fine lines, or
____________________________, on bullets. These striations will are
unique to the gun.
To determine that two bullets were fired from the same gun,
investigators examine both bullets with a comparison
microscope
to show that the striations match exactly.
NIBIN – National Integrated Ballistics Information Network
A program maintained by FBI and ATF to store and match images
from bullets and cartridges retrieved from crime scenes and test
fires of recovered weapons.
· More than 800,000 images stored
· Has matched more than 28,000 bullets or cartridges
· As with AFIS, any possible matches found must be verified by
an experienced forensic expert.
Gunpowder and Primer Residue
When a person fires a gun, gun powder and primer residue
typically blow back onto the shooter.
Gunpowder contains _____________________ – but so do many other
things including tobacco, some cosmetics, fertilizers, etc.
Now, investigators focus on looking for _____________________
and __________________ which are found in most gun primers (and are
less common elsewhere, though still present in brake linings and
fireworks).
Gunshot residue can be collected from suspects through
__________________________ or through ________________________ each
hand with cotton soaked in 5% nitric acid.
· Adhesive tape samples are first examined under a
_____________________________ _______________________________ –
gunshot residue has a characteristic size and shape. If the SEM
microscope is also attached to an ________________________ analyzer
then the elemental composition of the particles can also be
determined.
· Swabbing samples can be chemically analyzed but cannot be
viewed under the microscope.
Modern methods have greatly reduced the
______________________________ of gunshot residue analysis.
However, gunshot residue analysis still has a
________________________________________.
· Gun powder residue is easy to remove by washing hands and it
will typically wipe off within 2-6 hours after firing a gun.
· Primers for 0.22 caliber guns often do not contain barium or
antimony and so cannot be detected using traditional methods.
What is a false positive? A false negative?