Overview of forensic sciences final exam- 2025

Major Flexion creases of the palm

• Metacarpo phalangeal creases

  • separates the fingers

• Distal transverse

  • crease between index and middle finger

• Proximal transverse crease

  • under distal crease, middle of the palm

• radial longitudinal crease

  • Crease that separates the thumb

Regions of the palm

• Interdigital

  • upper finger portion of the palm

• Thenar

  • thumb side of the palm

• Hypothenar

  • outer part of the palm (pinky side)

5 Manners of death

• Natural

• Accidental

• Suicide

• Homicide

• Undetermined

Cause of Death

• the specific injury or disease that lead to death

Fingerprint Patterns

• Arch

• Loop

• Whorl

Age of a fingerprint

• You dont know the exact age of a fingerprint unless you see someone lay it

• sweat prints dry quickly, oil prints last longer

Statistical data (the odds of sharing a print)

• 1 in 64 billion

Matrix

• the composition of a fingerprint impression

• sweat, oil etc

Substrate

• the surface that the fingerprint is left on

• bottle, table, floor etc

• porous, non-porous

Latent

• invisible to the naked eye

Patent

• a print that is visible to the naked eye

aims of medicolegal death investigations

• determine cause/ manner/ time of death, identify deceased, collect evidence

DNA

• Deoxyribonucleic acid

• The genetic blueprint of life

• a long stranded molecule referred to as a double helix (twisted ladder shape)

• 23 pairs

Who can share DNA and prints

• identical twins share DNA and similar prints

Nuclear DNA

• in nucleus of a cell

• inherited from the mother and father

• 46 chromosomes

• longer

• more genes

• genetic makeup

Mitochondrial DNA

• found in the mitochondria located outside of the nucleus

• Mitochondrial DNA is inherited from the mother only

• 1 chroosomes

• shorter

• less genes

• metabolic activities

Police data banks AFIS

• automated fingerprint identification system

• used to identify individuals based on their fingerprint patterns

IBIS

• integrated ballistics identification system

• scan and digitally capture image

• linking firearm evidence

Layers of the epidermis

• Horny layer

• hyalin layer

• granular layer

• spinous layer

• basal layer

Spinous and basal layer named after malpighi

Estimations of post mortem interval

• Livor mortis

  • Blood settling

• Rigor mortis

  • Stiffening of the muscles

• Algor mortis

  • (cooling of the body)

Bodily fluids that florence under FLS

• semen

• urine

• saliva

• fingermarks

Trauma

• blunt force

• sharp force

• gunshot

Gunshot residue

• Contains barium, antimony, lead

Impression evidence

• objects or materials which have retained the characteristics of other objects or material which have been impressed against them (William J. Bodziak)

• footwear, tire, tool marks

Value of footwear impression evidence

• determine minimum number of suspects

• sex of offender

• age of offender

• types of shoe

Value of impression evidence continued

• where they went at the crime scene

• what they did at the crime scene

• where they went after

• identify the suspects footwear

• coroborate or refute witness/ suspect statements

What are bullets made of

• lead-antimony alloy encased in a soft brass or copper-plated soft steel jacket

DNA nucleotides

• Adenine (A)

• Thymine (T)

• Cytosine (C)

• Guanine (G)

Pairs of nucleotides

• Adenine and thymine

• Cytosine and Guanine

Types of evidence

• Inclusive

  • a person is included in an investigation- could have been there based on certain evidence

• Exclusive

  • they could not have been at the scene

• indeterminate

  • evidence that is not clear and precise can lead to multiple scenarios

four premises of the friction ridge identification

1. friction ridges develop on the fetus and their definitive form before birth

2. friction ridges are persistent throughout life, except for permanent scarring or disease

3. friction ridge patterns, and the small areas of friction ridges are unique and never repeated

4. overall, friction patterns within limits which allow for classification

barreling

• the process of creating or replacing a gun barrel

Rifilling

• the spiral pattern of land and grooves in the barrel of a firearm

forensic pathology

• sub-specialist in pathology with special competence in the examination of those dying suddenly, unexpectedly or violently

• performs autopies

• evaluates police investigative information

• collects medical evidence

• reconstructs how injuries were received

ridge unit

• a single section of ridge containing one pore

parameters for buried remains

1. immediate grave area

   • where the body is buried and a little extra of the surrounding area

   • how deep it is

2. scatter area

   • the furthest point you think the body was brought

where do insects colonize

• wounds or orifice

• if no wounds tight spaces like eyes, ears, genitals

Types of revolvers

• single action revolver: clocking the hammer '

  • the hammer must be manually cocked back before each shot

• double action revolvers: long trigger pull

  • pressing the trigger both cocks and the hammer

difference between a single and double action revolver

• Double action revolvers typically have a cylinder that swings open when a latch or button is pressed.

• single action revolvers do not have a cylinder that swings out

determening the exact distance of the barrel of the gun and subject

• impossible for exact determination

• possible for estimation only of likely ranges of distance from gun barrel to target

• GSR stippling indicates close range

Chromosomes

• 23 pairs of chromosomes

• 46 total

• including gender chromosomes x and y

Amylayes

• saliva holds the highest concentration of amyles 50x more than blood

Difference between rifles and shotguns

• difference between rifles and shotguns is the barrels and the type of ammunition

• rifles have rifled barrels for single accurate projectiles (bullets)

• while shotguns have smooth barrels for multiple projectiles (shot or pellets)

semi automatic and revolvers

• semiautomatic pistol

  • captures some hot gases produced by firing and use it to eject/ extract cartrdige cases (drive slide backwards) and simutaneously load new round into chamber

• Revolvers

  • single action

  • double action

What bodily fluids are most seen in forensic work

• blood

• semen

• urine

• saliva

• vaginal fluids

Types of shotguns

• semiautomatic

• lever action

• pump action

  • action refers to mechanism of cycling/ cocking the weapon

Types of rifles

• semiautomatic

• lever action

• bolt action

Track width

• can measure front and rear on a turn

• measurements made from the center of one wheel or impression to the opposite wheel or impression

Digital evidence

• digital images, videos, audio recordings, digital files, software

• any form of electronic data

Forensic serology

• the examination an analysis of bodily fluids

• used to find evidence of an identifiable body fluid, while DNA analysis seeks to accurately match those fluids to a specific individual

• forensically- determine its source at a crime scene

Types of bloodstain patterns

• pool

• spatter stains

• impact pattern

• impact pattern

• forward spatter pattern

• expiration pattern

• cast-off pattern

• projected pattern

• transfer stains

• swipe

• wipe

Pool

• a pool pattern indicated a blood source was in a location for a period of time

• typically at ground level, the longer they are on the ground the larger the pool of blood will get

spatter stains

• created when a blood drop is propelled through the air due to external force being applied to liquid blood

impact pattern

• an impact is created when an object strikes liquid blood

• Ex. hit someone on the ground the harder you hit them the further the bloodstain goes

Forward spatter

• a pattern resulting from blood drops which can be produced when a projectile creates an exit wound

• typically close range

Expiration pattern

• a pattern resulting from blood forced by airflow out of the nose, mouth or wound

• within the skin

cast-off pattern

• created when blood is released from a blood bearing object in motion

• swinging toward the person the pattern is going down, bringing it back pattern going up

• over the shoulder wind up

projected pattern

• created when a volume of blood is ejected under pressure

Transfer stains

• when a wet, bloodied object comes in contact with another object

swipe

• a swipe pattern is created when a blood bearing object is transferred onto another object with characteristics that indicate relative motion between the two surfaces

wipe

• a wipe pattern is created when an object moves through an existing bloodstain, removing it or altering its appearance

Bloodstain pattern categories

1. passive

2. spatter

3. transfer

Passive

• drip stains created when blood falls onto a surface due to the force of gravity

• if it is falling from a surface and you are static the stain will fall straight down at or around 90 degrees

spatter

• a drip pattern is created when a liquid drips into another liqued where at least one of the two is blood

transfer

• these stains occur when a surface wet with blood comes into contact with another surface, leaving a pattern or smear

Triangulation

• multiple cell towers within a radius, can reconstruct the route of the phone

Inculpatory

• include

• any evidence that will directly link an accused person to the offence being investigated. it can be anything from the direct evidence of an eyewitness to a fingerprint at the location

Exculpatory

• exclude- clears the suspect

• the exact opposite of inculpatory evidence in that it tends to show the accused person or the suspect did not commit the offence

Malware

• malicious software

• designed to harm, exploit, or compromise devices, networks or data

Hacking

• when the perpetrator breaks into a secure computer or network to commit a crime

phishing

• attackers, posing as legitamate entities use deceptive emails, text messages or phone calls to trick individuals into revealing sensitive information

Identity theft

• taking another persons identity

Fingerprint pioneers

• Marcello Malpigji

  • described several layers of epidermis, has a layer named after him

• Dr. Nehemiah Grew

  • first to describe friction ridge skin in detail

• Govard Bidloo

  • illustarted friction ridges and pore structures

• Dr. J.C.A Mayer

  • first to write that friction ridge skin is unique

• Alphonse Bertillon

  • created a method of identification through bodily measurements

• Sir William Hershel

  • used handprints as contracts first to use them for identification

• Dr. Henry Flauds

  • first to suggest using fingerprints in criminal case

• Sir Francis Gualt

  • first to define and describe fingerprint minutiae (galton details) dot, island, etc

• David ashbaugh

  • coined the term ridgeology (1982)

Fingerprint pioneers continued

• Juan vucetich

  • 1st murder to be solved with fp evidence

• Dr. Johannes E. Purkinje

  • classified fingerprints into 9 categories

• sir edward richard henry

  • developed fingerprint classification system (henry class system)

• Edward Foster

  • first fingerprint conviction in Canada

• Inez Whipple Wilder

  • published a paper on how friction skin is formed and why its unique

• Harris Hawthrone Wilder

  • first to suggest that disturbance of friction ridge formations is the location of volar pads

• harold cummins

  • noted that volar pad regression takes place with the beginning of friction ridge development

• Alfred Hale

  • explained differential growth of friction ridges

Friction ridge characteristics

• Minutiaw: ridge endings and bifurcations

Stages of the blowfly

• first- instar

  • hatched eggs

• second- instar

  • shedding

• third-instar

  • feeding

• puparial: metamorphoses

Directionality of blood

• term to describe the direction blood was traveling when impacted the target surface

• the tail of a bloodstain always tell the direction blood was going

• narrow end = direction of travel

  • Ex. narrow end facing right travel= left to right

head stamp on amunition

• manufacturer, caliber, lot number

Anthropometry

• the study of the measurements and proportions of the human body (bertillon’s body measurements)

Toolmark impressions

• quality of toolmark affected by substrate

• good

  • soft metals, plastics and painted surfaces

• Bad:

  • raw wood, hard metal

What is the first insect to attract to human remains

• blow flys

Composition of a fingerprint impression

• a print left from sweat made up of 99% water and the rest is grease, oil, salts and amino acids

Degree of impact to the shape of the bloodtstain

• perfect circle = 90 degrees stationary

• higher force=smaller spatter

Tracing

• uses an original signature or writing as a guide to produce a fraudulent document

• presence of guidelines around signature in pencil or carbon paper, indented impressions, poor line quality, uneven or wavy and drawn slowly difference in shading

free hand simulations

• attempt to draw the signature or writing of another person based on a model signature

• must maintain the same speed as the original writing, imitate correct letter formations, height ration, and pen pressure at the same time

• blunt starts and stops, pen lift line quality and connecting strokes

Normal hand forgery

• writes document in own writing style or attempts to distort it

• disguised writing

  • altering slant upper/ lower case changes print cursive etc

viscosity

• viscosity of blood 5x thicker than water

terminal velocity

• froce down = force up

surface tension

• slightly less than water

Locards exchange

• “every contact leaves a trace”

trier of fact

• judge or jury

Criminal law

• violations of federal statue or provincial legislation

• state vs individual

Civil law

• cases between individuals vs individuals and groups

• one company suing another or violating patent copyright

sipes

• thin slits in a shoe outsole or tire tread to create better traction

notches

• small void areas that extend off of groves or slots of a tire design but don’t fully cross the rib or tread block

treads

• the designed part of the tire that comes in contact with the road

grooves

• the space or channels that seperate the tread ribs and elements

• run across the circumfrence of the tire

What controls the activity of the sweat glands

• controlled by the autonomic nervous system

The growth of friction ridge skin

• pore ducts open along the top of the friction ridge

• these pore ducts appear to be evenly spaced

• this even spacing is caused due to the fact that the friction ridges are constructed of ridge units (fused together will form one friction ridge, each has a sweat gland and a pore opening all differential growth rate)

• each unit has one sweat gland and a pore opening randomly somewhere on its surface

• ridge units growing at different rates fuse together and form friction ridges

bone measurments

• an adult body has 206 bones

• baby approx. 300