Presentation on theme: "The Murder Scene: Death & Autopsies Chapter 2 O’Connor/Forensics."— Presentation transcript:
The Murder Scene: Death & Autopsies Chapter 2 O’Connor/Forensics
The body ► The most important piece of evidence in a crime scene that resulted in death is the body.
Who Investigates? ► Primarily the Forensic Pathologist Aided by: ► Forensic Anthropologist ► Forensic Entomologist
Role of Forensic Pathologist (in their role as coroner) ► They must answer these basic questions: ► Who is the victim? ► What injuries are present? ► When did the injuries occur? ► Why & how were the injuries produced? ► What is the cause of death? ► If observation can’t answer these questions, than an autopsy must be performed.
5 Classifications of cause of death ► Natural ► Homicide ► Suicide ► Accident ► undetermined
Remember!! ► Sometimes things are not as they first appear ► ex. Apparent suicide as murder cover-up. ► Sometimes things are simple and there is not more to it than what first appears. ► Ex. a rock near a body is just a rock, not a murder weapon
Estimating time of death ► After a human body expires it goes through several stages of decomposition. ► It is necessary to determine time of death in a crime.
Livor mortis ► a settling of the blood in the lower portion of the body, causing a purplish red discoloration of the skin: when the heart is no longer pumping the blood, heavy red blood cells sink due to gravity. This discoloration does not occur in the areas of the body that are in contact with the ground or another object. ► starts 20 minutes to 3 hours after death & is congealed in the capillaries in 4 to 5 hours. ► It can also be used by forensic investigators to determine whether or not a body has been moved.
Rigor mortis ► It commences after around 3 hours, reaching maximum stiffness after 12 hours, & gradually dissipates until approximately 72 hours after death. Rigor mortis occurs due to changes in the physiology of muscles when aerobic respiration ceases.
Algor Mortis ► the rate at which a body cools after death. ► affected by the physiology of the individual (age, weight, illness,) & the conditions of the environment (temperature, clothing, surface, activity prior to death). ► After the first hour to a period of about 6 hrs postmortem, a body will generally cool at the rate of 1.5° F for each hour after death. ► The preferred time window for evaluating algor mortis is within the first several hours after death. Beyond that, the rate of cooling becomes less & less accurate as the body temperature approaches equilibrium with that of its environment.
TOUR OF A MORGUE interactive at morgue with Dr. G interactive at morgue with Dr. G
Interactive Autopsy ► Discovery Health Autopsies Discovery Health Autopsies Discovery Health Autopsies
Forensic Anthropology ► Skeletal detectives ► Examination of bones may reveal: ► Sex, approximate age, race & skeletal injury. ► Used not only in crimes, but also for individual identification in mass tragedies, like a plane crash.
Computer Aided Reconstruction
1994 tourist disappearance
Body found in a shallow grave in Capetown
Forensic Entomology is the science of determining a time frame and/or circumstance from the empirical evidence of insect activity on or around the site in question. A time of death can be reasonably determined by factoring in ambient temperature, availability of corpse to insects, and the progress of blowfly larvae through their life cycle on that corpse. Approximately fourteen days is necessary for a blowfly to go from egg to adult.
Beetle Larvae ► are more variable in form than fly larvae, & there is more variation between species in the number of larval instars (stage of development between moulting) - up to fourteen. Beetles associated with carrion live in an ephemeral environment and tend to have short larval development times with only two or three instars. Most beetle larvae have chewing mouthparts and they feed on a variety of foods associated with corpses. ► Some are specialist predators, feeding on fly larvae, while others feed on dry flesh, skin, ligaments and hair.
Stages of decomposition as seen in piglets ► Why piglets? ► A 40 kg pig resembles a human body in its fat distribution, cover of hair and ability to attract insects. These factors make pigs the next best things to humans when it comes to understanding the process of decay of the human body. ► The pigs in this website are newborn piglets (weighing about 1.5 kg) that have been accidentally crushed by their mothers - a key cause of death of piglets. Their bodies have been donated to science.
Stage 1- living pig
Stage 2: Initial decay - 0 to 3 days after death
Stage 3: Putrefaction - 4 to 10 days after death
Stage 4: Black putrefaction - 10 to 20 days after death
Stage 5: Butyric fermentation - 20 to 50 days after death