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Friction Ridges and Fingerprints
Friction Ridges and Fingerprints
No two people have the same fingerprints
No two people have the same fingerprints
Not even identical twinsDemonstrates that fingerprints are
the result of both heredity and environment
Not even identical twinsDemonstrates that fingerprints are
the result of both heredity and environment
Forensic Fingerprints… history
Forensic Fingerprints… history
Cesare Lombroso - Theory of l’umo delinquente - late 1800’s
or The Criminal ManCriminals are evolutionary
throwbacks to primates
Cesare Lombroso - Theory of l’umo delinquente - late 1800’s
or The Criminal ManCriminals are evolutionary
throwbacks to primates
Lombroso said that criminals have certain
physical traits
Lombroso said that criminals have certain
physical traitsDoes that mean that some people
are “Natural Born Killers”?Lombroso thought so
Does that mean that some people are “Natural Born Killers”?
Lombroso thought so
Hence the need for more measurable ways to catch
a criminal
Hence the need for more measurable ways to catch
a criminal
Alphonse Bertillion - 1883- developed Bertillion Method - a complex system of body measurements
Anthropometric – Body measurements
Alphonse Bertillion - 1883- developed Bertillion Method - a complex system of body measurements
Anthropometric – Body measurements
First known use of Fingerprints in the United
States
First known use of Fingerprints in the United
States1902- City of New York, used
fingerprints on exams to prevent more well-educated persons from taking a civil service exam for the New York Civil Service Commission
1902- City of New York, used fingerprints on exams to prevent more well-educated persons from taking a civil service exam for the New York Civil Service Commission
First Homicide Conviction as a result of Fingerprint
evidence
First Homicide Conviction as a result of Fingerprint
evidence1911 - Thomas Jennings was
convicted of murder during a burglary in Chicago
1911 - Thomas Jennings was convicted of murder during a burglary in Chicago
International Association for Identification
International Association for Identification
Formed in 1915 - originally intended as a professional association for Bertillion Clerks
Changed to focus on fingerprints
Formed in 1915 - originally intended as a professional association for Bertillion Clerks
Changed to focus on fingerprints
1921 - Identification Division of the FBI
1921 - Identification Division of the FBI
Now the largest Identification Library in the world, housing more than 55 million criminal prints and histories
Now the largest Identification Library in the world, housing more than 55 million criminal prints and histories
Anatomy of Friction RidgesAnatomy of Friction Ridges
Appear on the palms, soles of feet and ends of fingers and toes
Are unique for the individual
Form in the 9th or 10th week of Fetal developement
Appear on the palms, soles of feet and ends of fingers and toes
Are unique for the individual
Form in the 9th or 10th week of Fetal developement
All Primates have Friction Ridges
All Primates have Friction Ridges
Friction Ridges enable us to grasp objects -
Friction Ridges enable us to grasp objects -
Primates also have nails instead of claws…claws would get in the way of holding onto objects
Primates also have nails instead of claws…claws would get in the way of holding onto objects
There are two main layers of our skin
There are two main layers of our skin
Epidermis is made up of mostly dead skin cells - 5 layers to epidermis…only
Stratum basale is alive and dividing
Epidermis is made up of mostly dead skin cells - 5 layers to epidermis…only
Stratum basale is alive and dividing
At 14 weeks sweat glands and ducts form in utero,
and form our Primary Friction Ridges
At 14 weeks sweat glands and ducts form in utero,
and form our Primary Friction Ridges
The interface between the dermis and the epidermis form secondary Friction
Ridges
The interface between the dermis and the epidermis form secondary Friction
Ridges
In looking at this image, Do friction ridges form
from the dermal layer or the epidermal layer?
In looking at this image, Do friction ridges form
from the dermal layer or the epidermal layer?
Friction Ridges or Fingerprints can be
classified as Patent or Latent
Friction Ridges or Fingerprints can be
classified as Patent or Latent
Patent if they are visible to the unaided eye - these appear when some material is present on the Friction Ridges and makes the print visible
Examples:Oily hand on clear glass, blood or paint
on fingers can also cause Patent prints
Patent if they are visible to the unaided eye - these appear when some material is present on the Friction Ridges and makes the print visible
Examples:Oily hand on clear glass, blood or paint
on fingers can also cause Patent prints
Latent PrintsLatent Prints
These require some assistance to make visible
Latent Prints are composed of the sweat or body oils that are transferred from the ridge pattern to some substrate
These require some assistance to make visible
Latent Prints are composed of the sweat or body oils that are transferred from the ridge pattern to some substrate
Fingerprint PersistenceFingerprint Persistence
> Fingerprints stick around for a long time
> On porous surfaces, paper, wood or cardboard, can last up to 40 years!!!! -as long as they aren’t exposed to water
On non-porous (metal, plastic etc.) surfaces can last even longer!
> Fingerprints stick around for a long time
> On porous surfaces, paper, wood or cardboard, can last up to 40 years!!!! -as long as they aren’t exposed to water
On non-porous (metal, plastic etc.) surfaces can last even longer!
Fingerprint classificationFingerprint classification
Friction Ridges form one of three basic patterns on each finger
Friction Ridges form one of three basic patterns on each finger
ArchesLoopsWhorls
ArchesLoopsWhorls
The Arch - Plain ArchThe Arch - Plain Arch
Tented ArchTented Arch
Loops - 60-70% of finger prints are loops
Loops - 60-70% of finger prints are loops
Whorls 25-30% of printsWhorls 25-30% of prints
Radial LoopRadial Loop
Double Looped WhorlDouble Looped Whorl
Double Looped WhorlDouble Looped Whorl
Two separate, distinct loop formations
Two separate, distinct loop formations
Central Pocket WhorlCentral Pocket Whorl
Any print with more than two deltas is an Accidental
Whorl
Any print with more than two deltas is an Accidental
WhorlA Delta is a triangleA Delta is a triangle
Composites include patterns in which combinations of the tented arch, loop and whorl are found in the same print, also patterns where the majority of ridges are loops and a few ridges
at the centre or side are whorls. These are subdivided into central pocket loops, double
loops and accidentals.
Composites include patterns in which combinations of the tented arch, loop and whorl are found in the same print, also patterns where the majority of ridges are loops and a few ridges
at the centre or side are whorls. These are subdivided into central pocket loops, double
loops and accidentals.
Central pocket loop.Central pocked loops are differentiated from whorls by placing the line of the glass across the two delta points. This line must not touch or cross any ridge formation within the inner area of aul pattern. (The inner pattern is that portion of the print contained inside both deltas.)
Central pocket loop.Central pocked loops are differentiated from whorls by placing the line of the glass across the two delta points. This line must not touch or cross any ridge formation within the inner area of aul pattern. (The inner pattern is that portion of the print contained inside both deltas.)
Double LoopDouble Loop
Double loop patterns consist of two separate loop formations, with two separate and distinct sets of staples and two deltas. They include the lateral pocket loop and twinned loop types.
Double loop patterns consist of two separate loop formations, with two separate and distinct sets of staples and two deltas. They include the lateral pocket loop and twinned loop types.
Primary Characteristics Recognized by the FBI:Primary Characteristics Recognized by the FBI:
Plain Arch Tented Arch Ulnar Loop Radial Loop Double loop (classified as a whorl) Whorl Central Pocket Whorl Accidentals (usually classified as a
whorl)
Plain Arch Tented Arch Ulnar Loop Radial Loop Double loop (classified as a whorl) Whorl Central Pocket Whorl Accidentals (usually classified as a
whorl)
1880 Dr Henry Faulds wrote to Charles Darwin asking for help in a fingerprint identification system
Sir Frances Galton - 1892“Finger Prints”
1880 Dr Henry Faulds wrote to Charles Darwin asking for help in a fingerprint identification system
Sir Frances Galton - 1892“Finger Prints”
Juan VucetichJuan Vucetich
Inspired by Galton’s book
Made first positive identification based on fingerprint - Francesca Rojas
Inspired by Galton’s book
Made first positive identification based on fingerprint - Francesca Rojas
Sir Edward Henry Sir Edward Henry
Was influenced by Galton’s book
1896 - developed the Henry Classification System
Was influenced by Galton’s book
1896 - developed the Henry Classification System
Henry Classification System
Henry Classification System
Primary Characteristics are assigned values
Primary characteristics; Arches, Loops, Whorls
Values come in the form of fractionsI.e. 1/13 or 23/2 - never reduced!!!
Primary Characteristics are assigned values
Primary characteristics; Arches, Loops, Whorls
Values come in the form of fractionsI.e. 1/13 or 23/2 - never reduced!!!
Each finger is assigned a value
Each finger is assigned a value
If a Whorl is present the value is inputed If No whorl is present a zero is put into the
equation
Ri/rt + rr/rm + lt/rl + lm/li + ll/lr + 1/1 =16 =8 =4 =2 =1
If a Whorl is present the value is inputed If No whorl is present a zero is put into the
equation
Ri/rt + rr/rm + lt/rl + lm/li + ll/lr + 1/1 =16 =8 =4 =2 =1
The Henry System can be used for Loops and Arches
as well
The Henry System can be used for Loops and Arches
as well
The Henry System should NEVER be used to identify
a person
The Henry System should NEVER be used to identify
a person
It is only used to rule out suspects It is only used to rule out suspects
The FBI uses the NCIC FPC system for identification
The FBI uses the NCIC FPC system for identification
Like the Henry system it cannot be a positive identifier
Used to rule out suspects
Like the Henry system it cannot be a positive identifier
Used to rule out suspects
Old FBI systems had problems transmitting Henry numbers
The NCIC FPC system was easier to transmit - no fractions
Old FBI systems had problems transmitting Henry numbers
The NCIC FPC system was easier to transmit - no fractions
NCIC FPCNCIC FPC
Number is a 20 digit alpha-numeric numberTwo characters are used for each finger
Begins with right thumb as number 1Left thumb is number 6…Left little is number 10
Number is a 20 digit alpha-numeric numberTwo characters are used for each finger
Begins with right thumb as number 1Left thumb is number 6…Left little is number 10
Which method is better?Which method is better?
FBI holds a little more information than the Henry SystemNumber of ridges on each loop What type of whorl, or loop
FBI holds a little more information than the Henry SystemNumber of ridges on each loop What type of whorl, or loop
Given an FBI fingerprint number you can calculate
a Henry number
Given an FBI fingerprint number you can calculate
a Henry number
But you cannot calculate a FBI number from a Henry number
But you cannot calculate a FBI number from a Henry number
Galton Details are also called Level 2 details
Galton Details are also called Level 2 details
They include formations in friction ridges such as ridge endings, bifurcations, dots etc.
They include formations in friction ridges such as ridge endings, bifurcations, dots etc.
Fingerprint MinutieaFingerprint Minutiea
Over 18 different minutiea points have been identified to help classify finger prints
Over 18 different minutiea points have been identified to help classify finger prints
A single individual may have upwards of 100 points that can be used as identification
A single individual may have upwards of 100 points that can be used as identification
Ridge DotsRidge Dots
A RIDGE DOT is a minutiea point that is an isolated ridge, whose lenth is equal to its width,
It is also called an island ridge
A RIDGE DOT is a minutiea point that is an isolated ridge, whose lenth is equal to its width,
It is also called an island ridge
BifurcationBifurcation
The point at which one ridge line divides into two ridge lines
This could happen in more than one way
The point at which one ridge line divides into two ridge lines
This could happen in more than one way
TrifurcationTrifurcation
A point where a ridge line splits into three different ridge lines
A point where a ridge line splits into three different ridge lines
Ending RidgeEnding Ridge
A point at which a ridge line endsA point at which a ridge line ends
Ridge CrossingRidge Crossing
Point where two ridges intersectPoint where two ridges intersect
Enclosure or “Lakes”Enclosure or “Lakes”
A point at which a single ridge bifurcates and re joins after a short course
A point at which a single ridge bifurcates and re joins after a short course
Spars or HooksSpars or Hooks
Bifurcation with a short ridge branching off
Bifurcation with a short ridge branching off
Bridge - a connection between two friction ridge
lines
Bridge - a connection between two friction ridge
lines
What is this?What is this?
What about this?What about this?
What is this?What is this?
What is this?What is this?
IAFISIAFIS
Integrated Automated Fingerprint Identification System
Integrated Automated Fingerprint Identification System
Largest Biometrics Database in the world
Largest Biometrics Database in the world
2 divisions
Criminal DivisionHouses 47 million criminal profiles
Civilian Division
2 divisions
Criminal DivisionHouses 47 million criminal profiles
Civilian Division
5 services of IAFIS5 services of IAFIS
1) 10 Finger Print Database of Identification10 rolled and 10 flat print database
1) 10 Finger Print Database of Identification10 rolled and 10 flat print database
2) Latent Fingerprint Services
2) Latent Fingerprint Services
Electronic and hard copies of latent fingerprints
Unidentified prints go to the unsolved cases fileMinutiea points are used to identify
unsolved cases
Electronic and hard copies of latent fingerprints
Unidentified prints go to the unsolved cases fileMinutiea points are used to identify
unsolved cases
3) Subject Search - Criminal History Index
3) Subject Search - Criminal History Index
Interstate index of criminalsParticipating states can search
interstate criminals’ records and histories
Responsible for updating criminal records
Interstate index of criminalsParticipating states can search
interstate criminals’ records and histories
Responsible for updating criminal records
4) Document and Imaging Services
4) Document and Imaging Services
Collects and distributes fingerprint related documents
Distributes Images Is capable of enhancing fingerprint
images… patent and latent
Collects and distributes fingerprint related documents
Distributes Images Is capable of enhancing fingerprint
images… patent and latent
5) Remote software support
5) Remote software support
Automated Fingerprint Identification System
Automated Fingerprint Identification System
Developed in 1999 as a new automated fingerprint system … a component of the original identification center with the FBI
Developed in 1999 as a new automated fingerprint system … a component of the original identification center with the FBI
IAFIS TechnologyIAFIS Technology
Can Enhance an image to improve its quality
Compare crime scene fingerprints against known 10 print records retrieved from database
Can Enhance an image to improve its quality
Compare crime scene fingerprints against known 10 print records retrieved from database
Cont.Cont.
Search crime scene fingerprints against known database when no suspects have been identified
Automatically search the prints of an arrestee against a database of unsolved cases --- so we can work backwards!
Search crime scene fingerprints against known database when no suspects have been identified
Automatically search the prints of an arrestee against a database of unsolved cases --- so we can work backwards!
How do they do what they do?
How do they do what they do?
The automated Fingerprint Identification System plots all the minutiea points (dots, ridge endings…)
It forms a Constellation
The automated Fingerprint Identification System plots all the minutiea points (dots, ridge endings…)
It forms a Constellation
Minutia plots are entered into a computer by a
scanner
Minutia plots are entered into a computer by a
scannerA typical X Y axis graph is
generated for the locations of the minutia
Once plot is made, individuals with similar XY coordinates are compared by a fingerprint examiner to make a positive identification
A typical X Y axis graph is generated for the locations of the minutia
Once plot is made, individuals with similar XY coordinates are compared by a fingerprint examiner to make a positive identification
What else can we tell by looking at a finger printWhat else can we tell by looking at a finger print
Race
Europeans and Africans are PRIMARILY Loops
Mongolians, Asians and Australian aboriginees are Primarily Whorls
Race
Europeans and Africans are PRIMARILY Loops
Mongolians, Asians and Australian aboriginees are Primarily Whorls
Your turn …Your turn …
Fingerprinting techniquesFingerprinting techniques
Whenever you touch something you leave a
Whenever you touch something you leave a
Colored Dust CollectionColored Dust Collection
Latent prints are dusted with colored powder
Powder sticks to oily depositsTape is placed over the print and
lifted by pulling the tape upChemicals can be sprayed on
surfaces like paper to develop prints
Latent prints are dusted with colored powder
Powder sticks to oily depositsTape is placed over the print and
lifted by pulling the tape upChemicals can be sprayed on
surfaces like paper to develop prints
NinhydrinNinhydrin
An amino acid detecting reagentAmino acids, subunits of proteinsAmino acids from your skin cells
would be deposited in the oily print
*Ninhydrin Must be used in the fume hood
An amino acid detecting reagentAmino acids, subunits of proteinsAmino acids from your skin cells
would be deposited in the oily print
*Ninhydrin Must be used in the fume hood
IodineIodine
Iodine Crystals are evaporated (only a small amount of heat is required)
As they evaporate, the brownish gas will react with fats to form blue black oil residue with the fingerprint
Remember: our hands do not sweat fats The oil comes from our face and hair
Iodine Crystals are evaporated (only a small amount of heat is required)
As they evaporate, the brownish gas will react with fats to form blue black oil residue with the fingerprint
Remember: our hands do not sweat fats The oil comes from our face and hair
Silver NitrateSilver Nitrate
Should be done LAST It removes the fats and proteins
(amino acids) that are necessary for Iodine, and Ninhydrin detection
Should be done LAST It removes the fats and proteins
(amino acids) that are necessary for Iodine, and Ninhydrin detection
AgNO3 + NaClAgNO3 + NaCl
Reacts with salts in sweat to form AgCl … a dark stain develops
Is a spray-able concoction that must be developed overnight Prints must be exposed to UV light before they appear.
Reacts with salts in sweat to form AgCl … a dark stain develops
Is a spray-able concoction that must be developed overnight Prints must be exposed to UV light before they appear.
CyanoacrylateCyanoacrylate
Known as “Super-gluing”.
Cyanoacrylate is the main ingredient in superglue
Used for hard, metal or glass surfaces.
Great with irregularly shaped objects
Known as “Super-gluing”.
Cyanoacrylate is the main ingredient in superglue
Used for hard, metal or glass surfaces.
Great with irregularly shaped objects
CyanoacrylateCyanoacrylate
Used in Suture-less surgeryUsed in Forensics with water vapor
– it polymerizes to form polyac rylate
Used in Suture-less surgeryUsed in Forensics with water vapor
– it polymerizes to form polyac rylate
Ninydrin PrintNinydrin Print
Cyanoacrylate “supergluing”Cyanoacrylate “supergluing”
Other PrintsOther Prints
EarsVoice- can be visualized on a
spectrographFootFaceShoes - prints can be compared to
a data base of known shoes (SoleMate)
EarsVoice- can be visualized on a
spectrographFootFaceShoes - prints can be compared to
a data base of known shoes (SoleMate)
Other Prints - Palm - friction ridges can be identified and used against suspects
Other Prints - Palm - friction ridges can be identified and used against suspects
Lips - display several patterns.
Lips - display several patterns.
Short vertical linesShort horizontal linesCrosshatchingBranching grooves
Short vertical linesShort horizontal linesCrosshatchingBranching grooves
Teeth - bite marks are unique and forensic odontologists can
determine an idividuals bite mark.
Teeth - bite marks are unique and forensic odontologists can
determine an idividuals bite mark.
Blood capsules in the eyes have distinct patterns that may be unique to individuals. These retinal scans are used today in some high tech security systems
Blood capsules in the eyes have distinct patterns that may be unique to individuals. These retinal scans are used today in some high tech security systems
Iris ScanningIris Scanning
Uses IR technology to trace the patterns of iris from the cornea
Uses IR technology to trace the patterns of iris from the cornea
Iris is flat Iris has unique pattern Iris set for life during embryonic
development – although scientists are still testing to see if patterns hold as we age
They are different between identicals
Iris is flat Iris has unique pattern Iris set for life during embryonic
development – although scientists are still testing to see if patterns hold as we age
They are different between identicals
EarsEars
Ears can be used to identify the living or the dead
They would be rolled and printed, or a latent print could be developed -
They would be classified
Ears can be used to identify the living or the dead
They would be rolled and printed, or a latent print could be developed -
They would be classified
Ears are classified byEars are classified by
SizeShapeFormAnatomical Distance between
different ear parts
SizeShapeFormAnatomical Distance between
different ear parts
Ear ClassificationEar Classification
Primary Classification is based on Race and Gender
Secondary Classification is based on 12 anthropometrical measurements of ear parts
Primary Classification is based on Race and Gender
Secondary Classification is based on 12 anthropometrical measurements of ear parts
After a print has been obtained, it will be sectioned off and
measured - this is the anthropemetrical center
After a print has been obtained, it will be sectioned off and
measured - this is the anthropemetrical center
In this way Ear Identification is based on
the Bertillion Method
In this way Ear Identification is based on
the Bertillion Method
After Ear measurements have been taken the print
is captured
After Ear measurements have been taken the print
is captured
Ears can be rolled and printedOr a Latent Ear Print can be
developedOr a cast can be made of an ear
print in a soft surface
Ears can be rolled and printedOr a Latent Ear Print can be
developedOr a cast can be made of an ear
print in a soft surface
Why would scientist go to such lengths to
characterize Ears?
Why would scientist go to such lengths to
characterize Ears?
Footprints are taken at birth as a means of
identification
Footprints are taken at birth as a means of
identification
Foot prints can be developed just like finger
prints
Foot prints can be developed just like finger
printsUsing dustNinhydrin IodineAgNO3Cyanoacrylate
Using dustNinhydrin IodineAgNO3Cyanoacrylate
What can we tell from a shoeprint?
What can we tell from a shoeprint?
Besides the brand you are wearing, forensic scientists can tell a lot more about you from your shoe print
Besides the brand you are wearing, forensic scientists can tell a lot more about you from your shoe print
Reebok, Nike, AllStar, Converse… shoes are a
dime a dozen right?
Reebok, Nike, AllStar, Converse… shoes are a
dime a dozen right?
Every brand has a specific pattern on the sole.
Every brand has a specific pattern on the sole.
SoleMateSoleMate
A database of shoe prints that holds of 12,500 different shoe prints
Dress ShoesCasual shoesAthletic sneakers It includes Manufacturer, brand,
version and prints of shoes
A database of shoe prints that holds of 12,500 different shoe prints
Dress ShoesCasual shoesAthletic sneakers It includes Manufacturer, brand,
version and prints of shoes
SoleMateSoleMate
Database is updated every 3 months, subscribers get a new CD in the mail with the updates.
Database is updated every 3 months, subscribers get a new CD in the mail with the updates.
www.crimeshoe.comwww.crimeshoe.com
Online data base of shoe prints. Not updated as regularly as
Solemate
Online data base of shoe prints. Not updated as regularly as
Solemate
Unlike Earprints, Shoe prints are admissible in a court room as evidence
Unlike Earprints, Shoe prints are admissible in a court room as evidence
A new law, as of 2004, allows investigators to confiscate suspect shoes without a search warrant
A new law, as of 2004, allows investigators to confiscate suspect shoes without a search warrant
Three parts to a shoe, Tread, sole and cushionThree parts to a shoe,
Tread, sole and cushionTreads are the portion of the shoe
that leaves the impressionsThey are the grooves that line the
sole (impressions may be patent or
latent)
Treads are the portion of the shoe that leaves the impressions
They are the grooves that line the sole
(impressions may be patent or latent)
Patent Prints might occur if person walks across
mud, dirt, paint or blood
Patent Prints might occur if person walks across
mud, dirt, paint or blood
Prints are photographed with a ruler next to it.
Photos taken at 90 degrees
Prints are photographed with a ruler next to it.
Photos taken at 90 degrees
Latent Shoe PrintsLatent Shoe Prints
Can be dusted to emphasize details
Developed with cyanoacrylate
Why wouldn’t Ninhydrin or AgNO3 work?
Can be dusted to emphasize details
Developed with cyanoacrylate
Why wouldn’t Ninhydrin or AgNO3 work?
Casts can be madeCasts can be made
Impressions are 3-D imprints in mud sand, clay or snow
Dental stone to make a cast – to preserve impression.
Impressions are 3-D imprints in mud sand, clay or snow
Dental stone to make a cast – to preserve impression.
When casting in snow…When casting in snow…
Dental Stone gives off heat as it sets
A substance called Snow Print Wax is applied first to set the print.
Dental Stone gives off heat as it sets
A substance called Snow Print Wax is applied first to set the print.
What else can we tell from a person’s shoeprint?
What else can we tell from a person’s shoeprint?
A person’s gait can be determined based on the wear pattern
A person’s gait can be determined based on the wear pattern
Shoe prints can determine a person’s height
Shoe prints can determine a person’s height
Your foot is roughly 15% of your full height
Your foot is roughly 15% of your full height
Do they pronate or supenate?
Do they have collapsed arches?
Do they walk on the balls of their feet?
What part of the soles are worn away?
Do they pronate or supenate?
Do they have collapsed arches?
Do they walk on the balls of their feet?
What part of the soles are worn away?
If a walking pattern is visible, you can determine if a person is heavy or thin
If a walking pattern is visible, you can determine if a person is heavy or thin
How far apart are the footprints How far apart are the footprints
What is the difference between a print and a
cast?
What is the difference between a print and a
cast?3 D versus 2 DCasts can be made of
impressions, but not of printsThe Impression is a negativeA cast is a positive of a shoe print
3 D versus 2 DCasts can be made of
impressions, but not of printsThe Impression is a negativeA cast is a positive of a shoe print
Foot wear impressionsFoot wear impressions
What factors will affect impressions?Weight of individualSurface print is left on
Some surfaces will imprint better than others
What factors will affect impressions?Weight of individualSurface print is left on
Some surfaces will imprint better than others
Some soils will give a better impression than
others
Some soils will give a better impression than
othersClay-based soil will give the best
impressions, as clay has a very fine texture
Clay-based soil will give the best impressions, as clay has a very fine texture
How to make a cast…How to make a cast…
Investigators always take a photograph first, in case the casting ruins the print
Investigators may spray their cast with darkly colored spray to enhance details
Investigators always take a photograph first, in case the casting ruins the print
Investigators may spray their cast with darkly colored spray to enhance details
When choosing Casting material consider the
following
When choosing Casting material consider the
following Material should have capacity to show
fine detail Material should be easy to make and
cheap Material should flow easily into
impression without disrupting print Material should set in reasonable time Material should be easily cleaned and
stable
Material should have capacity to show fine detail
Material should be easy to make and cheap
Material should flow easily into impression without disrupting print
Material should set in reasonable time Material should be easily cleaned and
stable
Professionals use Dental Stone
Professionals use Dental Stone
Plaster of Paris also works, but investigators no longer use it because it is so hard to clean
Plaster of Paris also works, but investigators no longer use it because it is so hard to clean
How to make the print…How to make the print…
Step 1) Mix your dental stone to the consistency of pancake batter
Step 2) Locate your impression Step3) Pour the dental stone next
to your print. Do NOT pour the dental stone into the print, it may disrupt print
Step 4) Allow 30 minutes to set
Step 1) Mix your dental stone to the consistency of pancake batter
Step 2) Locate your impression Step3) Pour the dental stone next
to your print. Do NOT pour the dental stone into the print, it may disrupt print
Step 4) Allow 30 minutes to set
Applications of Biometrics…
Applications of Biometrics…
Allowing people access across State borders
Computer securityTheft protectectionEtc.
Allowing people access across State borders
Computer securityTheft protectectionEtc.
Accuracy v.s. PrecisionAccuracy v.s. Precision
What does it mean to say your measurements are Accurate?
What does it mean to say your measurements are Accurate?
