The term forensic stems from the Latin word forum and a applies to anything that relates to law. Forensic science or Criminalistics is the application of scientific disciplines to the law.
Every contact you make with another person or object results in an exchange of physical materials.
Known as the Locard Exchange Principle after Dr. Edmond Locard, the French police officer who first noticed it, the exchange of materials is the basis of modern forensic investigation. Using this principle, forensic scientists can determine where a suspect has been by analyzing trace evidence fibers or clothing, hair in a car or junk on the soles of shoes.
Medical Examiners and Coroners
Coroners and Medical Examiners are charged with determing t he cause and manner of death, overseeing the e analysis of evidence and presenting their findings in court.
The coroner or ME (medical examiner) often works with the police to help guide their on going investigations by supplying them with the results of any forensic tests that have been preformed.
The responsibilities of theses two offices cover every aspect of investigating a death.
The terms coroner and ME are often used interchangeably but they are actually quite different.
A coroner is an appointed or elected position that formerly required no special medical or forensic skill.
A ME on the other had is a medical doctor that has specialized training in forensic medicine.
Manner of Death
The manner of death is an opinion expressed by the ME based upon all the circumstances leading to and surrounding the death. The ME's opinion may or may not be accepted by the courts, law enforcement, lawyers or the victim's family. Even if the ME concludes that a death was a homicide, prosecutors may disagree and file no charges. Likewise surviving family members may sue the coroner?s officer for any number or reasons to change the manner of death particularly a death that has been ruled suicide.
The Forensic Investigator
The forensic investigator is an extension of the ME. He or she is the Me's representative at the crime scene and works with the ME at the morgue.
The investigator deals w with the body at any crime scene where death has occurred. As an extension of the ME, the forensic investigator has legal authority over the body.
The Forensic Investigator may:
Make a cursory examination of the body
Obtain a core body temperature which is critical in determing the time of death
Direct the taking of photographs of the body
Collect any trace or insect evidence from the body
Wrap and transport the body to the ME's office
Primary and Secondary Crime Scenes
Crime Scenes are considered primary or secondary. The primary scene is where a crime actually occurred. A secondary crime scene is in some way related to the crime but not where the actually crime took place.
Primary scenes typically yield more usable evidence than do secondary scenes but not always. Sometimes the only crime scene investigators have to work with is a secondary scene--the place where a serial killer dumps a victims body for example.
Normal clotting time for blood is 3 - 15 minutes, but clotting time is extremely individual and can be affected by certain diseases such as hemophilia and some leukemia?s and various medications including blood thinners
When bl first begins to clot it forms a dark shiny jelly like mass, with time the clot begins to contract and separate from the yellowish serum.
Investigators use the state of blood clotting as a rough guide to estimate how much time has passed since the blood has shed. If it's a shiny gelatinous pool bleeding occurred less than an hour earlier and if the blood is separated into clot and serum, several house have probably passed.
The mechanisms by whish blood leaves the body can be divided into two categories, passive and projected. Passive bleeding depends upon the action of gravity alone. This kind of bleeding includes oozes and drips. Blood is projected when en a person or object applies some force other than gravity. Arterial spurts, cast off blood and impact spatter are examples of projected blood.
Passive blood stains form not because of force but because of the laws of gravity. Blood that oozes or gushes from the body moves downhill and collects in the lowest areas on or near the injured or deceased person. Gushing or fast-flowing blood obviously gathers in larger amounts and can travel farther from the body than oozing blood. A slow ooze clots before blood moves to far from the body.
each droplet in a blood spatter strikes t he surface from a unique direction and at a unique angle. The impact angle is the slant at which the blood drops strike the surface and the directionality is the course the blood drop followed.
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 the crime scene investigators stretch strings from each stain according to an angle of impact where those strings meet is the point of convergence.
Point-of-Origin a three dimensional representation of the point where lines tracking not only the pathways but also angels 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, investigators can find the point of origin.
A void pattern is an absence of blood spatters in an area where you'd otherwise expect to see them. Often this void indicated where the attacker stood because his body prevented the blood from spattering on the surface behind him.
Investigators classify blood spatters in one of two ways.
By velocity-This method of classifying blood spatters looks not only at the velocity at which the impacting object strikes the blood source but also the velocity at which the blood leaves the blood source when it's stuck. These subcategories give an indication of the object and the mechanism that created the spatter.
By type of Spatter-Impact spatters typically occur with beatings, stabbings, gunshots or any other circumstance where a foreign object impacts the victim. Projection spatters result from arterial bleeding, cast off blood and expiated or exhaled blood, combination spatters which include impact and projection spatters often are found at crime scenes. A victim who gets stabbed in the chest or neck may leave a combination of impact spatters from the force of the attack and projection spatters from arterial bleeding, expiated blood and cast off blood.
A blood stain associated with an entrance wound is called blow back or back spatter. Meaning the droplets travel in a direction opposite to the path of the bullet.
Transfer patters restful when an object soaked with blood comes into contact with an unstained object.
Cause of Death
Cause of death is the reason the individual died. Heart attack, gunshot wound are causes of death. They are the disease or injuries that alter the victim's physiology and lead to death.
The mechanism of death is the actual physiological change or variation in the body's inner workings that causes the cessation of life.
Entry and Exit Wounds
The character of a wound produced by a gunshot depends upon several factors including the distance between the victim and the muzzle of the gun.
The caliber and velocity of the bullet, the angle at which the bullet enters the body.
Whether the bullet remains within the victim or passes completely through exiting the body (a through and through gunshot wound) the ME can estimate the distance from which a single bullet was fired by looking closely at the entry wound.
If the muzzle was two or more feet away from the victim, the entrance wound usually is a small hole with an abrasion collar (a blue-black bruising effect in a halo around the point of entry)some black smudging my occur where the skin literally wipes the bullet clean of the burned gunpowder, grime and oil residue it picks up as it passes through the barrel of the gun.
If the muzzle was between 6 inches and 2 feet from the point of entry the skin may appear tattooed or stippled. This effect is the result of tiny particles of gunpowder discharged from the muzzle embedded in the skin causing tiny hemorrhages in a speckled pattern around the wound.
If the muzzle was less than 6 inches from the victim, the gunshot produces a hole a compact area of stippling, a surrounding area of charring and a bight red hue to the wounded tissues.
If the muzzle is pressed against the victim when the gun is fired hot gasses and particulate matter are driven directly into the skin, producing a greater charring and ripping the skin in a star-shaped or stellate pattern.
Sharp Force Wounds
Sharp force wounds can be divided into three general types:
Stab Wounds- Stab wounds usually are deeper than they are wide. They are also more likely to be distorted by the victim's twisting and turning to fend off an attacker.
Incised or cut wounds are caused when a sharp instrument is drawn across the skin. Unlike stab wounds they have no characteristic width or depth and thus reveal little of the nature of the weapon. These wounds are rarely fatal but when they are usually are suicidal or homicidal.
Suicidal wounds typically are found on the victim's wrists and rarely on the neck. Suicidal incised wounds frequently are accompanied by hesitation marks.
Homicidal incised wounds typically are seen on the neck. If the assailant is behind the victim, the cut usually extends from high up on one side near the ear, sweeps downward across the front of the throat and then back up the opposite side. The path of the is sweep is left to right in a right handed assailant and the opposite for a left-handed one. If an attacker is facing a victim, the cut usually is shorter and on an angle. Defensive wounds may be incised in nature. As a victim attempts to fend off an attacker. The knife blade may slice the victim's hands, wrists, forearms and even feet
Accidental cuts typically involve the hands and rarely are fatal. Accidental cuts that involve the neck are extremely rare. Falling or flying glass fragments make up the majority of such neck wounds.
Chop wounds are produced by heavy, sharp edged implements such as axes and meat cleavers. these wounds tend to be deep and wedge shaped. fractures and grooves often are seen in underlying bones. Lethal chop wounds usually are accidental or homicidal and rarely suicidal
Blunt Force trauma occur whenever you make contact with a hard dull object in a way that hurts you. Abrasions are injuries that result in the removal of the superficial layers of skin.
Sliding Abrasions occur when an object scrapes or brushes away the skin.
Stamp Abrasions occur when a blunt object strikes the skin crushing it and leaving behind a raw area. These types of abrasions tend to be small and discreet and may reflect the general shape of the object that made them.
Pattern abrasions are special type of stamp abrasion where the blunt object that strikes you leaves behind its pattern or the pattern of clothing or any other material between the object and your skin.
The healing process can be divided into five stages:
Scab formation begins almost immediately but is not noticeable until after about 6 hours. The wound may ooze serum for the first 24 hours. Red blood cells are usually caught up in the dried red-brown serum that becoThe abradarea appears dark red and when viewed under the microscope reveals the presence of large humbers of specialized white blood cells.
Cell regeneration which is the reappearance of lost epithelial cells begins about 36 hours after the injury but isn't clearly visible until after about three days. Regeneration begins at the edges of the injured area. Cell growth and thickening progresses during the next 5 days. The cells divide, grow in number and continue the healing process.
Remodeling occurs by about day 12 when the skin has thinned and taken on a slightly pale appearance.
The skin completes its repair and all remnants of the wound disappear, leaving a bleached out color. Over the next few months the pigment regenerates. The skin regains its normal appearance by about day 20
Abrasions inflicted after death have a characteristic color and character that identify them as postmortem injuries. Because circulation has stopped, blood cells and serum don't accumulate at the injury so these scrapes take on a light brown parchment like appearance. If the abrasion occurs in an area of Lividity it may show some red discoloration but cutting into the tissue will reveal the absence of hemorrhage.
Contusions or bruises result from damage to small blood vessels in tissue at the site of a blunt-force trauma. These injured vessels leak blood, which imparts a blue-black color to the tieeues. Blood collecting in a pocket beneath the skin is called a hematoma.
Fractures are breaks in bones that result from direct or indirect trauma. A simple fracture is a single break. A comminuted fracture is where the bones breaks in two or more places. A compound fracture is one in which the bone protrudes through the skin.
When an object makes direct contact with a bone it causes either a single transverse fracture one that occurs across the long axis of the bone or a crush fracture one that is composed of several fracture lines. A crush fracture often produces a compression wedge which can indicate t he direction of blows. The wedge points in the direction of the corce. Knowing the direction of helps the ME reconstruct the blow and perhaps even the sequence in which multiple injuries occurred. In automobile pedestrian accidents this type of fracture often is termed bumper fracture because it results from the impact of a vehicle's bumper against the victim's legs or arms. Indirect fractures are not caused by a direct blow to the bone but rather occur when an indirect force is applied to the bone with sufficient force to cause it to break. Traumatic indirect fractures are divided into four basic types
Angulations fractures are simply transverse fractures that occur when a bone is bent to the point of breaking which may occur when someone falls while their arm is trapped or held stationary. This type of injury commonly happens to children playing on playground monkey bars.
Rotational fractures arise when a bone is twisted causing spiral fracture that twists down the long axis of the bone. The direction of the spiral indicated the direction of the twisting force. A child yanked or thrown by the arm may suffer such fractures.
Compression fractures result when force is applied along the long axis of the bone, driving the bone into it's end resulting in a T or Y shaped break common in automobile accidents in which the victims knee is driven into the dashboard.
Combination fractures are any combination of angulations, rotational and compression fractures.
Time of Death
Unless the death is witnessed it is impossible to determine the exact time of death. The legal time of death is the time the body was discovered or the time a doctor or other qualified person delclared the victim dead.
Physiologic time od death is when vital functions altually cases.
The Medical Examiner (ME) can estimate the physiologic time of death with some degree of accuracy. He uses the decompositional changes that occur in the human body after death.
Typically a body cools at the rate of approximately 1 to 1 1/2 degrees per hour until it takes on the temperature of it's surroundings.
An obese person tends to cool more slowly than someone with little body fat.
By 24 - 36 hours after death the smell of rotting flesh appears and the skin takes on a progressive greenish-red color. By 3 days gas forms in the body cavities and beneath the skin which may leak fluids and split. Add to this predation by animals and insects and the body can become completely skeletonized before long. In hot humid climates this can happen in 3 or 4 weeks.
The general rule regarding decomposition is that 1 week on dry land = 2 weeks for a submerged body.
Bodies tend to sink th en rise again in several days when the gas forms adding buouyancy, under these circumstances the hands and feet swell(several days) the outer layer of skin separates from the underlying tissues (5-6 days) the skin of the hands and the nails separate (8-10 days) and entire body swells shortly thereafter. Tissue become extermely fragile.
A body will float after 8-10 days in warm water and 2-3 weeks in colder water. Cold slows the process.
Drops in body temperature
In theory a body cools at a regular rate after death.
The rate depends on ambient temps
Clothing and environmental factors
Illness or drugs may rise temp prior to death
Size/weight of body alters estimates
This is the dark blue discoloration that is observable on the parts of the body, which are nearest the ground. The blood settles under its own weight into the lowest parts of the body. This coloring appears about two hours subsequent to death. After the blood has settled it tends to clot in the tissue. Even if the body is moved after death the Lividity remains. If the body is found with postmortem Lividity on the upper surface it can be concluded that the body was moved after death. It is important to differentiate between discoloration due to Lividity and that due to bruises. Close observation will reveal distinct differences:
A) The bruises may have a swelling or abrasions, Lividity does not have these indications.
B) The color of the bruise is variable, that of Lividity is uniform
C) Lividity appears only on the low-lying parts of the body, bruises may appear on any part.
D) In the case of Lividity, an incision will reveal the facts that the blood is still in the vessels, in bruises an incision shows that blood has broken out of the vessels.
The muscles of the body stiffen after death because of the chemical changes that take place within the muscle's tissue. Immediately after death, the body is limp and relaxed. A relaxing of the sphincters lead to incontinence. With the onset of rigor mortis the body becomes exceptionally stiff. The stiffening process begins at the neck and lower jaw and spreads downward. All the muscles voluntarily and involuntarily, including the heart muscles, contract.
A) Time Required--Rigor mortis may begin to set in 15 minutes after death or 15 hours after. On average, it commences in about 5-6 hours; after which the upper part of the body is affected within 12 hours and the whole body within about 18 hours.
B) Duration-Rigor mortis usually disappears within 36 hours. The head and neck once more become relaxed and the limpness gradually extends to the lower parts of the body. The process may take from 8-10 hours.
C) Estimating time of death- Many variables enter into the speed with which rigor mortis sets in and disappears. The investigator must employ the following rough rules:
1) Rigor mortis should begin within 10 hours after death.
2) The whole body should be stiff within 12-18 hours after death
3) Stiffening disappearing within 36 hours after death.
D) Cardaveric Spasm--Sometimes stiffening occurs immediately after death. This happens when there is a severe injury to the central nervous system or when there was great tension at the moment of death.
If the eyes remain open after death a thin film forms on the surface.
The potassium content from the break down of red blood cells enters the eyes and within two through three hours, they look cloudy.
Eyes that are closed develop the same condition but it takes much longer, cloudiness may not occur for an entire day
This is based on an assumption that the stomach digest food and empties into the intestines at a predictable rate
Many things can influence this process. The type of food, the body's metabolizing rate, the presence of drugs or medications and the person's emotional condition prior to death may all have some effect on how fast food is processed.
(secondary patterns of postmortem change)
Byers narrowly defines autolysis as the dsgcnation of body tissues by the liberation of digestive fluids of the intestinal tract.
Decomposition is a mixed process ranging from call autolysis due to internal chemical breakdown to tissue auytolysis due to liberated digestive fluids.
Animal predators from maggots to coyotes also contribute significantly to the process of decomposition.
General stages are fresh, early and they advanced decomposition followed by skeletonization and then exterme decomposition
Initial decomposition rate depends on conditions of the body and the environment
It usually begins 2-3 days in unrefriderated corpses.
Putrefication is a force of decomposition cause by mocroorganisms in the body.
Skin slippage is a sign of early decomposition
Fluids including plasma build up under skin where body rests
Ruputre of connective tissues casuses loss of epidermis and loss of attached hair, also nails loosen glove formation occurs as skin slippage proceeds.
Discoloration also occurs in early decomposition.
Initially a green discoloration of abdominal wall due to proliferation of normal flora in the gut.
Marbling occurs when internal bacterial colonize venous system resulting in hemoloysis of blood which appears darker.
The body goes gray to green to dark with the face and extermities turning color first.
Darker color often occur in conjunction with bloating (usually 1-8 weeks)
Bloating is part of early decomposition occurs as swelling of tissues during release of gasses in autoysis to bacterialr espiration
Generally appears at 2-8 days postmortem especially in the face.
Can cause bluding of tongue and eyes and extrusion of feces.
Froathing or foaming of blood from trachiea also observed
After bloating reach a point bloating state with rupture of adominal cavity from gasses and dark color
Advanced decomposition includes liquafication, possible adipocere formation and possible mummification.
Liquidifaction results as fat liqufies in abdominal and thoraic cavities.
Causes sagging of flesh and caving-in of abdominal catiey.
Adipocere formation is the formation of grave wax due to hydrogenation of lipids can occur in conjunction with liquidfaction, skeletonization, mummification or some combination there of.
Typically occurs in cooler, wetter enviornments (caskets, downing victims, burials) with less open air exposure.
Common in arid environments
Drying precedes or interrupts decomposition
Body mositure less than 50%(bacterial growht arrested)
Skin becomes hard and leathery but underlying tissue can remian moist until dehydration turnns t hem into a think jelly-like consistency
Partial mummification in 10 days - 1 month
Total desication in 2 months -18 months
Skeletonization is accelerated or retarded by environmental animal and insect activity, exposure (buried or not buried)
Initial occurences in head and heand
Areas of trauma also skeletonize faster
Typically can occur in 3 months (but as fast as 14 days) to over 3 years
Bleacing of bone (exterme decomposition typically occurs in 9 months to 3 years)
Exfoliation of the outer layers of the desicated cortical bone occurs around 3 years
Variables affecting decay rates are (from most to least influential)
1)Temperature-humidity and access by insects
Hot weather can lead to accelerated liguefaction
Cold slows decay and changes skin color to black/orange
Low humidity increases insect activity and liquefaction
Low humidity increases mummification
insects are an important factor affecting rates of decomposition and skeletionization
They initially invade fact and orifices in wwarm weather they reach the body in seconds
2)Burial and depth of burial or impersion in water
Decompostion rates or buried individuals is about 8 times slower than unburried body.
Prevents access by insects and carnivores at depth greater than 1-2 feet insects and carnivors cannot smell remains.
soft tissue decomposition depends on the moisture of the soil and the presence of soil organisms such as plant roots and bacteria, adipocere occures in wet soil.
Survival of buried skeleton once the soft tissue has decayed depends on the ph of the soil and its moisture content.
Solis that are highly acidic or alkaline or are saturated with water will rapidly cause the destruction of most of the skeletal tissues.
immersion in water increases skin slippage and prevents mummification. acted on by marine carnivores when deposited in salt water.
Soft tissue decompostion is retarded in a water enviornment but the exposed portions of the body will attract insects and undergo the same sequence of decomposition including maggot activity as a body on the ground.
Decompostion takes about twice as long if a body is submerged in water than if it is on the ground.
Resurfacing and decomposition rate of body depends on temperature, salinity and bacterial load of the water
once the body resurfaces, the exposed portion will be invaded by insects and decomposition will progress rapidly
If a body is submerged for long periods of time adipocere formation will occur. Autopsy
An autopsy is a postmortem examination of a corpse to determine manner and cause of death. Around 25% of all deaths are subject to it including homicides, cases of sudden infant death syndrome (SIDS)overdoes, industrial accidents etc.
The following is a list of some of the essential facts that an autopsy may establish:
A) The probable cause of death
B) An estimate of the time of death
C) The number and nature of the wounds on the body.
D) The identity of the fatal wound
E) Whether the wound was self-inflicted
F) The kind of weapon used
G) An estimated time elapsed between receiving the wound and death.
H) An assessment of the victims ability to move after receiving the wound
I) The probable manner of death
J) The blood type
K) Evidence of alcohol or drug use
L) Evidence of sexual assault
The manner of death falls into one of five categories:
Any deaths not the result of natural causes such as disease or expiring in bed from old age should be investigated, even natural deaths may be investigated if caused by contagious disease that could harm the community.
All childhood deaths are investigated as are deaths of people in the public eye.
Body discovery scenes outside are categorized by how the body is found, buried, exposed or submerged in water.
If the body is buried, soil samples are tested for the presence of added substances such as quicklime.
Bodies lying exposed may have parts missing due to scavengers attacking the corpse.
Bodies found in water where boats are present may have injuries from propellers.
With body discovery scenes inside the crime scene is generally more preserved, although the corpse may have been dismembered and stored someplace for a long period of time.
At the scene the Death Investigator(DI) briefly examines the body and makes some preliminary notes and diagrams. He must avoid disturbing any trace evidence that might linger on the corpse.
Only the coroner authorizes body transport
The body gets removed by lifting and wrapping it in a clean white sheet to preserve all evidence. The body is then placed into a body bag for transport.
Injuries are generally categorized as blunt force trauma, gunshot, and sharp force trauma.
In all cases the number or wounds is recorded and each would in carefully measured and it's characteristics are described.
1) A blunt force injury comes from impact with a blunt object or something with no sharp edges. ME's determine the direction of impact, the type of object that caused it and how often the contact was made
Wound examination is done with care.
Crushing wounds result from blunt violence where the skin is close to the bone, these wounds tend to bleed into the tissue. Often they're made by blows from a hammer or ax head.
Bite marks are also a form of crushing wounds.
2) With gunshot wounds the coroner looks for tattooing and stippling around the wound.
A shot gun blast makes its own distinct pattern.
The ME also measures the size of the exit and entry wounds and extracts any bullets left in the body in order to determine the type of gun they came from.
Contact wounds in which the gun was held against the skin often leave an imprint from the muzzle and more powerful guns cause gaping wounds with powder residue and blow-back hot gases from the gun that fail to penetrate the body and blow back to the exterior ripping the skin.
Entrance wounds are generally round and surrounded by some abrasion.
Exit wounds are irregular bruised without stippling and larger than the entrance wound.
3) With a knife or incised wounds the coroner must make a distinction between cut and stab or puncture wounds and among different types of piercing implements such as an ice pick or small knife.
A cut is larger than it is deep while a stab wound is deeper that it is long.
Most knife have a flat edge and a sharp edge which can be seen in the wound angels.
Some wounds are defensive such as cuts made on the palms or fingers of a victim's hands.
Cuts associated with suicidal gestures are known as hesitation wounds as the person attempts to inflict self-damage
Source Information--The Forensic Science of CSI Katherine Ramsland 2001 Berkely Publishing Group source information--Forensics for Dummies D.P. Lyle MD 2004 Wiley Publishing