Exam 2 | Forensic Science
whorl
- 34% - Ridges that make a 360 degree circle - 2 deltas
arches
- 6%, ridges enter one side of the finger and exit the other side of the finger - Rarest - No cores or deltas
loop pattern
- 60% - Ridges enter one side, loop around, and exit the same side it enters - one delta and one core
Questioned Documents
- Any object that contain handwritten or printed material, whose source is unknown -It can be any material, not just paper (graffiti, suicide note on mirror or wall) Ex: handwritten notes, types notes, copied papers, printed papers
How do you examine a machine printed document?
- Classify a possible make and model for the investigation - Identify a questioned document to known machine - Matches made based on defects
What is being determined when looking at questioned documnets?
- Compare Handwriting - Determine Author - Is the document Authentic? - Can this help and give an INVESTIGATIVE LEAD
Handwriting Comparison
- Compare unknown with known exemplar - No standards/set number needed to prove similarity (just like fingerprints) -Therefore, we cannot use probabilities or statistics is not allowed
Tool mark comparisons
- Examiners should know how tools are made and used - Test marks might be compared to questioned marks
finger print history
- Fingerprints used to be used to mark clay pots - First used for identification in NYC in 1902 - Identification Division of the FBI was established in 1924
Handwriting of Individuals
- Handwriting habits formed at young age - As you grow, there are gradual changes - Physical/emotional state can effect handwriting - You can't determine age, insanity, or gender by handwriting
Individualization of Handwriting
- Learn to write by copying model letters - Penmanship/ different ways ppl hold pens - Handwriting becomes subconscious and unique
Features on the Ridge (level 3)
- Location of Sweat pores - Ridge thickness - Scars or something that disrupts ridge pattern
Tire Tread
- Part that comes in contact with the road -Few unique characteristics so once again, look for wear, use, imperfection, embeddings
How to preserve prints
- Photography: Final image should be 1:1 to allow for accurate comparison -Collect surface if possible
Collecting Requested Exemplars
- Phrase things a certain way (dictating what you want them to write) - Passages should be long - Same type of writing instrument
negative impression
- Removing the surface to replace with the print Ex: Stepping in mud and leaving behind shoe impression
Indented Impressions can be examined with _________ and ____________
- Side Lighting -Electrostatic Detection Device (EDD)
Things to look for when comparing handwriting
- Spacing between letters - Space between words - Size of letters - Slanting - Pen lifts - Connective strokes - Beginning/ending strokes - shading - baseline
Serial Number Restoration
- Stamped into metal which alters the CRYSTAL structure -Acids (destructive) - Magnaflux: magnut (not destructive) Always start with this one! - After restored it must be photographed or else it will fade
Types of Unnatural Writing/ Forgery
- Tracing: following the outline. Literally tracing - Simulation/Blind: know what it's supposed to look like and you reproduce it - Distortion: writing that does not appear to be , but may be natural due to factors (age) - Disguise: deliberately altering writing intended to hide the identity of the writer by changing habits
Forgery Characteristics
- Unnatural appearance (looks like a drawing) - Lack of individuality - Slowly written - MANY PEN LIFTS - Correction mistakes - Tell if something has been traced - Inconsistent letters - No rhythm
Can impression evidence lead to individualisation?
- YES, but not all... (might not always be able to find a unique pattern) Ex: print is blurry/unclear, new material that has not wear/tear, common pattern
positive impression
- adding a print onto a CLEAN surface -Latent prints & patent prints are a positive impression Ex: Ink, Blood, Paint
What is involved in ink examination?
- determine instrument used - how many inks were used (VSC) - look for obliteration - look for indentations (ESDA)
latent prints
- invisible, 2D; require assistance (develop them) to make them visible. -Composed of sweat and oils that is transferred to a surface/reciprocate
non-requested exemplar
- know who wrote it but not what they used (ink) or what they wrote on Ex: Diary Entry, check, legal document, letter, notes from notebook
do friction ridge patterns change during your life
- no; Friction Ridges are developed in the uterus at 14 weeks and at 15 weeks they are completely formed - all primates have friction ridges
friction ridges
- the unique markings on the fingertips, handprints, footprints that leave oily marks on surfaces we touch - Allows us to grasp things - located in the dermis
plastic prints
- visible to naked eye, 3D, made in a soft surface - negative impression (Molding or casting of the print, Stepping in mud)
Lifting Imprints
-2D impressions can be lifted with a powder and tape lift -Can't lift grease, oil, blood, or carpeting
Firearms vs Ballistics
-Ballistics: study of an object in flight and is part of physics. This is trajectory -Firearm Identification: involves the analysis of marks in bullets or cartridge cases due to the mechanisms within the weapon, force needed to fire the bullet
Unique Characteristics Of Footwear (Class and Individual)
-Class: left/right, brand of shoe, overall pattern, size of shoe -Individual: Wear patterns (loss of traction) and imbedded materials (rocks)
Comparing Footwear
-Compare positive to positive and negative to negative. -Compare 3D to 3D and 2D to 2D -No set number of unique characteristics
Casting Footwear
-Dental stone: primary material used for casting because it hardens fast and captures details. This material is more dense, has smaller particle size, and dries quickly -Plaster of Paris: soft, even after drying, made of large particles which prevents the cast from being detailed
3 factors that determine how to preserve/enhance impression...
-Depends on location, 2D, 3D -If possible, remove print and take to lab -If you cant remove it, take a cast
What do Firearm Examiners do?
-Exam cartridge casings rather than bullets (bullets are hard to find and are damaged) -Use tests to determine is a weapon has been fired -Can estimate distance of shooting incidents -Chemically restore serial numbers -Test items/people for GSR (gunshot residue) -Analyze patterns on injury-wound ballistics
Signatures
-Harder to find specifics -Signatures often unreadable
Why might footwear be over looked?
-Nearly invisible -Bad location -Trampled on -Misunderstood/undervalued by CJS
How can you preserve Footwear?
-Photograph print with and without ruler -In 2D, photo will be used for comparison -In 3D, footprints are casted. The casting material (plaster/dental stone) will fill the impression and harden to capture the impression
Types of firearms
-Pistols: Self loading/revolvers -Rifles - Revolvers (do not release cartridges) -Shotguns (do not have lands/grooves) -Machine Guns -Submachine Guns
How do you find footwear at a Crime Scence?
-Use tools to find latent footwear -Oblique lighting, dusting (same as in fingerprint analysis)
3 methods for collecting tire impressions
1. Photographs 2. Drawing 3. Casting/Tape Lifts
How to find Latent Fingerprints
1. Use alternate light sources: Blacklight, Laser Light 2. Use chemicals: Iodine, ninhydrin, superglue, Cyanoacrylate Fuming 3. Use Powders: powder will stick to the oils left behind
when were fingerprints first used
1902; prisons/jails
Are exemplars known or unknown?
ALWAYS KNOWN
What is being looked for during ink examinations?
Alterations Obliterations Erasures
NIBIN is a computer system used to compare...
Both bullets and cartridge casings
Tire Impression Casts
Casts are made with dental stone and are bulky/hard to handle (you can also take lifts)
Tools for bullet comparison
Comparison microscope (Look at 2 things at once)
Henry Classification
Henry Classification = Even number finger values + 1/ odd number Finger Values + 1 -Only count the fingers that have a whorl present on that finger -DO NOT REDUCE FRACTION.
Video Spectral Comparator (VSC)
IR light: either the ink will do nothing, ink will become transparent, ink will glow/fluoresce
Ink Jet vs Toner
Ink Jet: liquid and absorbs Toner: granular, shiny, dry and melted onto paper
Striations are produced from what part of the barrel/bullet?
Lands in barrel, grooves on bullet
hard surfaces
Leave 2D impressions (blood, ink, dust)
Identification Levels Level _____ & _____ can be used for identification, but not level ____!
Level 1: General Ridge Pattern Level 2: Ridge Formation Level 3: Details on the ridge 2 & 3; 1
Tire Treads vs Footwear
Much larger/longer than footwear
If a chemical exam of ink is needed, where must one go to get it done and why?
Must go to IRS, Homeland Security, or Secret Service. This is because chemical examinations are destructive.
Do toolmarks have to have a certain number of similarities?
NO!
Is there a standard number of matches needed for impression evidence?
NO!
Visual Records of Footwear
Photo video Sketch Location
minutiae/ridge formation
Ridge Ending Enclosure Bifurcation Island
What is a toolmark?
Scratch or microscopic marking that is left behind by a tool/object
Obliterations in QD can include......
Staple holes Paper Ink
Rifling
The spiral pattern of lands and grooves in the barrel of a firearm
Bertillonage
This method failed when there were 2 William wests in the same prison and it was too hard to identify them
Machine Printed Documents can be made from _________ ________ __________
Typewriting Photocopies Printers
2 types of loops
Ulner loops: enter and exit closest to ulner bone (pinky) Radial loops: enter and exit toward radial bone (thumb)
Physical Developer vs Superglue fuming
Used on oils, waxes, lipids, fats Superglue (cyanoacrylate) coats fingerprint ridges with hard, whitish coating - binding to proteins in the print. Now the fingerprint can be treated with chemicals or powder
Can toolmarks be individualized?
YES! we are looking for imperfections over time
Can exemplars be used in court?
YES! requested AND nonrequested can be used in court
Are tire treads often overlooked?
Yes
3 Components of GSR
barium, antimony, lead
Galton
first person to scientifically study fingerprints and he developed the method still used today - Tried to find the likelihood of finding 2 friction ridge patterns that are the same
Lands in a brrel create _______ on bullet. Grooves in barrel create _____ on bullet
grooves;lands (lands contain striations and therefore lands are used as individual evidence)
soft surfaces
leave 3D impressions (putty, mud)
3 ridge patterns
loop, whorl, arch
Blind Forgery (Simulated)
made without a model of the signature (going based off memory)
Can you tell personality/age from handwriting? When looking at machines, one is looking for ________ and _______. ______ and _______ look for modifications/obliterations.
no defects and flaws VSC;ESDA
can ALL impression evidence lead to individulization
nop
donor
object making physical contact (tire treads, shoeprints)
Traced Forgery
one made by tracing a genuine signature
striated marks
parallel to recipient surface
impressed toolmarks
pattern in a perpendicular angle to the surface
Exemplar
representative example, this is used to compare to the unknown document
2 types of exemplars
requested and Non-requested(collected)
tented arch
sharp peak in the center (like a tent pole)
Ink impression of Tire Treads
take a tire, cover in ink, roll it out
requested exemplar
tell them what to write, what to write with, and what to write on
recipient
the surface that receives the characteristics from the donor (soft and hard surfaces)
Disguided Writing
trying to make it look like you didn't write something (use wrong hand, use block letters/capital letters, irregular spacing)
Friction ridges are considered _____________ even though there is a small chance there are similar prints because of all the possibilities
unique
patent prints
visible to the naked eye, 2D, recipient would be a hard surface. Adding print to the surface
Straited toolmarks
when tool marks do not hit at a perpendicular direction (parallel instead) -wrench
Impressed Toolmark
when tools hit the surface at a perpendicular direction (Hammer)
