Forensic Principles I

What damages to bone are characteristic of canines ?

A "v" shaped injury Punctures Pits Scoring Furrows

What is the pattern for arterial bleeding ?

A freely spurting artery results in a linear and cascading spatter pattern

Friction ridge skin

A layer of skin that is unique to the Palmar surfaces of the hands and the Plantar surfaces of the feet The depressions between the ridges are called furrows. Friction ridge skin is thicker than other skin and contains more nerve endings

What should always be included in photographic evidence ?

A scale

Define point of origin

A three-dimensional representation of the point where lines tracking, not only the pathways, but also the angles of impact of two or more spatters meet, indicating the general spatial location of the blood source. By stretching strings along the angle of impact of each stain, the point of origin can be found. Points of Origin can indicate whether a victim was standing, sitting or laying when the blood-shedding trauma occurred

Define point of convergence

A two dimensional representation of the point where lines tracking the pathways of two or more spatters meet, indicating the general location of the blood source in relation to the spatters. At a crime scene, strings are stretched from each stain according to direction of impact. Where those strings meet is the point of convergence

When does the diameter of a blood pattern stop increasing significantly?

After 7 feet

What are the three types of time of death ?

Algor mortis Rigor mortis Livor mortis

Define void pattern

An absence of blood spatters in an area where you'd otherwise expect to see them. This void may indicate where an attacker stood because his body prevented the blood from spattering on the surfaces behind him

Define expert witness

An individual whom the court determines possesses knowledge relevant to the trial that is not expected of the average layperson They may be able to offer an opinion that is based on a reasonable scientific certainty derived from training and experience

Define a accidental manner of death

An unintentional death resulting from an injury and/or poisoning , such deaths typically being unforeseen and not predictable as to time and place of occurrence (also death from drug use)

Putrefaction

Anaerobes : 96-99%of bacteria in colon, bacteroides, clostridia Aerobes: 1-4% enterococci, proteus

Physical developer

Another silver-based developer which reacts to form a dark gray reaction. Useful on paper, cardboard and unvarnished, light-colored woods. It is very successful on items exposed to water.

Define cause of death

Any injury or disease that produces a physiological derangement in the body that results in the individual dying

Adhesive (sticky) side powder

Attaches itself to plastic print impressions on adhesive side of tapes. Produces excellent results on light-colored or transparent tapes, including duct tape, masking tape, plastic surgical tape, foam tape, clear and reinforced packing tapes and labels. Process involves wetting tapes.

Types of decomposition

Bloating Mummification Adipocere formation

Postmortem coagulation

Blood becomes acidic from tissue breakdown Causes activation of intrinsic coagulation pathway Clots in arteries and veins As decomposition progresses pH decreases activating fibrinolysis Eventual re-liquefaction of blood

Back spatter vs Forward spatter

Bloodstain associated with an entrance wound is called Back Spatter, the droplets travel in the opposite direction of the path of the bullet, often found on the shooter or weapon Forward Spatter is a high-velocity spatter found at an exit wound. In the case of forward spatter, blood droplets follow the direction of the bullet

Postmortem eye changes

Clouding of cornea Tache noir: dark band of dried epithelium on the eye ( occurs within a couple hours ) Sludging and intravascular coagulation of retinal vasculature

Central Pocket Loop

Consists of at least one recurving ridge, or an obstruction at right angles to the direction in which the pattern flows. It has two deltas, between which, when an imaginary line is drawn, no recurving ridge within the pattern area is cut or touched.

Lateral pocket loop "lazy loop"

Consists of at least one recurving ridge, which flows into a pocket formation of ridges, and flows out or tends to flow out from the same side from which they entered. It has one delta

Whorl fingerprint

Consists of one or more ridges that make a complete circuit, with two deltas, between which, when an imaginary line is drawn, at least one recurving ridge is cut or touched

Twinned (double) Loop

Consists of two separate loop formations with two deltas.

Accidental

Contains two or more distinct types of patterns with the exception of the plain arch, with two or more deltas, or a pattern that has some of the requirements for two or more different types, or a pattern that conforms to none of the definitions 65% of fingerprints are loops , 5-10% arches, remainder are whorls

1,8 Diazafluoren-9-one (DFO)

DFO is a fluorescing ninhydrin analog found to develop up to two and a half times more prints than ninhydrin. Useful on porous surfaces, especially paper. Development may be accelerated through the application of controlled heat. Developed prints require the use of an alternate light source for viewing

Define suicide in terms of a manner of death

Death due to a self-inflicted act that was meant to do harm or cause one's own death

Define a natural manner of death

Death results solely from disease and/or the aging process and no external cause(injury or poisoning) contributed to death

Algor mortis

Decrease in body temperature after death

What can decrease gastric emptying time ?

Diabetic neuropathy

Factors that may effect the characteristic or minutiae of a fingerprint

Dirt Pressure Distortion Uneven distribution of transferred material Technique used to develop latent print

Postmortem changes

Distortion of facial features Distention of abdomen and scrotum Gas bubbles may be seen in liver and other solid organs Purge fluid: decomposed gastric lining and contents

Define homicide in terms of a manner of death

Due to the volitional act of another person that is meant to cause harm, injury, fear or death or as a result of wanton disregard for human life

What are the three types of minutiae ?

Ending ridge, Bifurcation (dividing ridge), and Dot.

Who is Karl Rokitansky ?

Famous pathologist who developed a method of performing autopsies in which he would open all organs in situ

Who is Rudolph Virchow ?

Famous pathologist who developed a method of performing autopsies in which he would remove organs individually and then dissect them

Scientific identification is based on what ?

Fingerprints Dental Nuclear DNA Mitochondrial DNA

Latent impressions

Fingerprints left at a crime scene, which are invisible, or partially visible to the naked eye.

Patent impressions

Fingerprints left at a crime scene, which are visible to the naked eye These impressions are made by fingers contaminated with substances such as blood, ink, grease or dirt. They may also be left when fingers are pressed into plastic surfaces such as putty, tar, adhesive-coated surfaces, wax, and cheese

Mummification

Fluid loss via evaporation Extremes of hot and cold Skin is hard, leathery, forms a shell Exposed parts of the body: fingers ,toes, face

What are the stages of decomposition ?

Fresh Early Advanced Skeletonization

What can accelerate the fixation of lividity ?

Heat, sepsis , and heart failure

Conditions that can accelerate decomposition

Hot environment Overweight decedent Sepsis Hyperthermia

Define manner of death and what are the 5 types ?

How the cause of death came into being Types includes: Natural Accident Suicide Homicide Undetermined

Postmortem change-autolysis

Hydrolytic enzymes released by lysosomes Triggered by a decrease in intracellular ph Digest carbohydrates and proteins Digest fats to a lesser degree Begins sooner in organs with abundant lysosomes Bullae formation

What kind of pattern is created when a blood droplet strikes a surface at less than 90 degrees ?

If the drop strikes from a smaller angle, the spatter creates an elongated oval pattern, with the narrow or pointed end aiming in the drop's direction of travel

What can delay the formation of lividity ?

Internal and external hemorrhage and cold temperatures

Iodine fuming

Iodine fumes react with oils and fatty deposits to produce a temporary yellow-brown reaction. Useful on fresh prints on porous and non-porous, non-metallic surfaces. Developed prints must be fixed or photographed immediately because reaction will rapidly fade.

Adiopocere formation

Malodorous cheesy compound May occur in a few days if warm and moist Formation requires lipids (i.e. in the brain or skin) Longer periods in a dry environment Hydrolysis and hydrogenation of fats to fatty acids

Embalming artifacts

May have multiple incisions for replacement of arterial blood with embalming fluid may be misinterpreted as antemortem stab and cut wounds Abdominal perforation which is used to place embalming fluid in the abdominal cavity and is usually closed with a embalmer's "button" can mimic a gunshot wound Very difficult to diagnose a pulmonary embolus in an embalmed body because of the clotting of blood that embalming fluid causes

Products of decomposition

Methane Hydrogen Hydrogen sulfide Carbon dioxide Alcohol: ethanol due to decomposition is usually found in the blood only and not the vitreous or urine Ammonia Putrescine Cadaverine Biliverdin (green) Bilirubin (red) Urobilin (brown) Hydrogen Sulfide (black)

Where is rigor mortis more evident ?

Most evident in smaller muscles and gradually becomes evident in larger muscle groups i.e. Jaw, upper ext,lower ext Involves all muscles at the same time and at the same rate

Tented Arch Fingerprint

Most of the ridges enter on one side of the fingerprint and flow out or tend to flow out the other side: however, the ridges at the center form an angle, an upthrust, or possess two of the basic characteristics of a loop, lacking the third.

Ninhydrin

Ninhydrin reacts with amino acids to produce a purple reaction product called "Ruhemann's Purple". It is useful on porous surfaces-especially paper. Development time is up to 10 days, but may be accelerated through the application of heat and humidity. Not useful on items which have been exposed to water.

Define an undetermined manner of death

No determination regarding manner can be made after an autopsy and investigation

Medium velocity spatter

Occurs from objects moving between 5 and 100 feet per second. These spatters are typically smaller than low-velocity spatters, varying from 1 to 4 mm. in diameter. Created by impacts with blunt or sharp objects, and possibly expirated blood

Low-velocity spatter

Occurs when an object traveling less than five (5) feet per second strikes a surface. The impact results in fairly large spatters, typically greater than 4 mm. Produced by such mechanisms as drops dripping from a wound or blood-soaked clothing or weapon. Arterial bleeding is considered low-velocity

Loop fingerprint

One or more of the ridges enter on one side of the pattern, recurve, touch or press an imaginary line between delta and core, and flow out or tend to flow out on the same side from which they entered. Right slanted loops flow toward the right. Left slanted loops flow toward the left

What are the different types of powders used to recover fingerprints

Pigmented Fluorescent Magnetic Powders adhere to water and fatty deposits. Generally useful on newer prints only They are useful on any dry, relatively smooth, non-adhesive surfaces. Choose a pigmented powder to contrast with the background

Methods of latent print recovery

Powders Chemical Processes Alternate Light Sources Mechanical Processes

Fluorescent Powders

Powders made of fluorescent materials offer advantages to the limitations of conventional powders They are applied the same as with pigmented powders Especially useful on confused backgrounds Lifts can be made photographically or by conventional means. An ultraviolet or alternate light source is required.

Tardieu spots

Pressure of lividity ruptures blood vessels causing skin hemorrhages Takes about 18-24 hours Indicates decomposition is rapidly approaching Larger than petechiae

What damages to bone are characteristic of rodents ?

Produce parallel striae Pedestal phenomenon: epiphyseal cartilage and adjacent areas of long bones May use human bone for nesting purposes May transport bone

Livor mortis

Purple/red discoloration in the dependent areas of the body due to accumulation of blood after cardiac activity has ceased Begins between 30 minutes to 2 hours after death Reaches maximum at 8-12 hours Usually "fixed"or unblanchable by 12-18 hours after death Inappropriate lividity patterns or locations may suggest a body has been moved after death Can occur internally especially in the lungs

Amido black

Reacts with proteins found in blood to form a black reaction. Useful only on blood-contaminated prints. Highly sensitive Useful on non-porous and some slightly porous surfaces. Sometimes offers successful development of blood prints on dead human skin.

Silver Nitrate

Reacts with the chlorides in skin secretions to form silver chloride, a material which turns gray when exposed to light. Prints must be photographed immediately because the reaction will eventually, and permanently, fill the background. Useful on paper, cardboard, plastics and unvarnished, light-colored woods. It is not useful on items which have been exposed to water.

High velocity spatter

Result from an object striking a victim at a speed faster than 100 feet per second, and from expirated blood. tend to be very small, usually less than 1 mm. and appear as mist-like stains. Most associated with gunshots

Define transfer patterns

Result when an object soaked with blood comes into contact with an unstained object. This includes bloody fingerprints, shoeprints, etc.

How can canines effect remains ?

Results in disarticulation and scattering of remains Produces artifacts Alter antemortem injuries Removal of soft tissue of face and neck Destruction of ventral thorax and upper extremities,clavicles Lower limbs detached Disarticulation of longs bone Disarticulation ,gnawing and scattering of all or most bones

Plain Arch Fingerprint

Ridges enter from one side of the pattern and flow or tend to flow out to the other side with a slight rise or wave in the center

Small particle reagent (SPR)

SPR is a suspension of fine molybdenum disulfide particles. They adhere to fatty components of skin secretions to form a gray deposit Developed prints must be photographed immediately due to the reaction product being very fragile Developed prints may be carefully lifted using conventional methods. SPR is useful on relatively smooth, non-porous surfaces, including wet surfaces

Spatters can be produced by several different mechanisms

Stabbings Beatings Gunshots Arterial bleeding Cast-off blood Splashing Expirated blood

Rigor mortis

Stiffening of muscles after death, due to a lack of ATP in the muscle Resolution of rigor results from detachment of actin from the ends of the sarcomere causing the contractile unit to lengthen again Usually begins 2 to 4 hours after death , usually resolved by 36 hours Can be broken by passive stretching of muscles Rigor mortis may be inconsistent with gravitational forces indicating that the body was moved

Cyanoacrylate (superglue) Fuming

Superglue fumes polymerize on fingerprints to form a hard, whitish deposit. This process is accelerated when the superglue is exposed to heat and elevated humidity. Most useful on non-porous and some porous surfaces. It produces excellent results on styrofoam and plastic bags.

Scars

Temporary scars generally have sharp edges. Permanent scars generally have edges that are curled and puckered

Define impact angle

The angle at which the blood droplet strikes the surface Impact Angle is determined by using the bloodstain's width to length ratio.

Locard's Exchange Principle

The exchange of materials between two objects that occurs whenever two objects come into contact with one another Believed that every criminal can be connected to a crime by dust particles or "trace evidence" carried from the crime scene

What is the pattern associated with cast-off ?

The spatter pattern associated with cast-off blood tends to be a fairly uniform trail of droplets, which reflects the arc in which the object traveled

Define marbling

This is an autolysis PM change. postmortem spread of bacteria within the vasculature caused by the bacterial production of hydrogen sulfide interacting with hemoglobin produced by postmortem red cell hemolysis

Define skin slippage

This is an autolysis PM change. release of hydrolytic enzymes at dermal epidermal junction

Order of tissue decomposition

Tissue with more blood , decomposes quicker Intestines, stomach, heart, blood, digestive organs Air passages and lungs Kidneys and bladder Brain and nervous tissue Skeletal muscle Connective tissue

Define directionality

Used to make Point of Convergence and Point of Origin determinations.

Post mortem chemical changes

Vitreous potassium: increases as time since death increases Highly variable Controlled by rate of decomposition

What is the terminal velocity of blood ?

approximately 25 ft/s at approximately 25 feet

What do projection spatters typically result from ?

arterial bleeding, cast-off blood, and expirated blood.

Presumptive identification

based on circumstances, location of body, possessions found near body

Scientific identification

based on physical or molecular characteristics that a person cannot alter

What do impact spatters typically occur with ?

beatings, stabbings, gunshots, or any circumstance where a foreign object impacts the victim

What causes cherry red lividity ?

carbon monoxide poisoning, cyanide poisoning, fluoroacetate and cold temperatures

How does ambient temperature effect rigor mortis ?

cold temperature accelerates and prolongs rigor while warm or hot temperatures delays it ( in warm weather rigor may never fully develop)

Define fixed livor mortis

cooling solidifies dermal fat and closes capillaries so blanching of skin can not occur-- person dead for longer duration

What causes green lividity ?

hydrogen sulfide

What causes minimal lividity ?

hypovolemic shock or anemia

What are cathepsins?

proteolytic enzymes which can increase the release of the actin from the sarcomere allowing for the resolution of rigor

Define post-mortem ejaculation

rigor mortis in muscle of seminal vesicles

Define gooseflesh

rigor mortis in muscles of hair follicles

What kind of pattern is created when a blood droplet strikes a surface at a 90 degree angle ?

the splatter pattern forms an even circle around the point of impact

How do surfaces effect blood spatter ?

•Hard, smooth surfaces like glass, tile , or polished marble create much smaller patterns than rough, irregular surfaces like unfinished wood or concrete.