Post-mortem dissection, or autopsy, was among the earliest scientific methods to be used in the investigation of violent or suspicious death. Autopsy remains the core practice of forensic medicine. The postmortem examiner surveys the body's surface, opens it up with surgical instruments, removes parts for microscopic inspection and toxicological analysis, and makes a report that attempts to reconstruct the cause, manner, and mechanism of death. These clips from training films show some of the procedures of postmortem examination. Tools of the trade The post-mortem examiner visually surveys the body's surface before opening and entering the body with the help of a scalpel and other instruments. After visual examination of the body cavities, the examiner removes parts for chemical analysis, inspection with a microscope, and other tests. Tools and tool kits specially adapted for use in autopsy first appeared in the early 19th century. Forensic specimens For centuries, anatomical specimens from the bodies of crime victims have been used as teaching tools and souvenirs of interesting or important cases. These specimens demonstrate various types of traumatic wounds of the heart, kidney, and stomach. They were prepared in the 1930s by the New York City Medical Examiner's Office.

On April 14, 1865, the assassin John Wilkes Booth shot President Abraham Lincoln during a performance at Ford's Theatre in Washington, DC. After the President passed away on the following morning, his body was placed in a temporary coffin covered with an American flag, and returned by hearse to the White House, accompanied by a cavalry escort. At the White House, an autopsy was performed by Army Surgeons Edward Curtis and Joseph Janvier Woodward. Also in attendance were Surgeon General Joseph K. Barnes and a few military officers, medical men and friends. During the autopsy Mary Todd Lincoln sent a messenger to request a lock of hair; a tuft was clipped from the head for her. Dr. Curtis described the autopsy in a letter to his mother: Dr. Curtis described the autopsy in a letter to his mother: "The room…contained but little furniture: a large, heavily curtained bed, a sofa or two, bureau, wardrobe, and chairs….Seated around the room were several general officers and some civilians, silent or conversing in whispers, and to one side, stretched upon a rough framework of boards and covered only with sheets and towels, lay—cold and immovable—what but a few hours before was the soul of a great nation. The Surgeon General was walking up and down the room when I arrived and detailed me the history of the case. He said that the President showed most wonderful tenacity of life, and, had not his wound been necessarily mortal, might have survived an injury to which most men would succumb….Dr. Woodward and I proceeded to open the head and remove the brain down to the track of the ball. The latter had entered a little to the left of the median line at the back of the head, had passed almost directly forwards through the center of the brain and lodged. Not finding it readily, we proceeded to remove the entire brain, when, as I was lifting the latter from the cavity of the skull, suddenly the bullet dropped out through my fingers and fell, breaking the solemn silence of the room with its clatter, into an empty basin that was standing beneath. There it lay upon the white china, a little black mass no bigger than the end of my finger—dull, motionless and harmless, yet the cause of such mighty changes in the world's history as we may perhaps never realize.…[S]ilently, in one corner of the room, I prepared the brain for weighing. As I looked at the mass of soft gray and white substance that I was carefully washing, it was impossible to realize that it was that mere clay upon whose workings, but the day before, rested the hopes of the nation. I felt more profoundly impressed than ever with the mystery of that unknown something which may be named 'vital spark' as well as anything else, whose absence or presence makes all the immeasurable difference between an inert mass of matter owning obedience to no laws but those covering the physical and chemical forces of the universe, and on the other hand, a living brain by whose silent, subtle machinery a world may be ruled. "The weighing of the brain…gave approximate results only, since there had been some loss of brain substance, in consequence of the wound, during the hours of life after the shooting. But the figures, as they were, seemed to show that the brain weight was not above the ordinary for a man of Lincoln's size." Dr. J.J. Woodward's autopsy report, April 15, 1865 [A]ided by Assistant Surgeon E. Curtis, U.S.A., I made…this morning an autopsy on the body of President Abraham Lincoln, with the following results: The eyelids and surrounding parts of the face were greatly ecchymosed and the eyes somewhat protuberant from effusion of blood into the orbits. There was a gunshot wound of the head around which the scalp was greatly thickened by hemorrhage into its tissue. The ball entered through the occipital bone about one inch to the left of the median line and just above the left lateral sinus, which it opened. It then penetrated the dura matter, passed through the left posterior lobe of the cerebrum, entered the left lateral ventricle and lodged in the white matter of the cerebrum just above the anterior portion of the left corpus striatum, where it was found. The wound in the occipital bone was quite smooth, circular in shape, with bevelled edges. The opening through the internal table being larger than that through the external table. The track of the ball was full of clotted blood and contained several little fragments of bone with small pieces of the ball near its external orifice. The brain around the track was pultaceous and livid from capillary hemorrhage into its substance. The ventricles of the brain were full of clotted blood. A thick clot beneath the dura matter coated the right cerebral lobe. There was a smaller clot under the dura matter [sic] of the left side. But little blood was found at the base of the brain. Both the orbital plates of the frontal bone were fractured and the fragments pushed upwards toward the brain. The dura matter [sic] over these fractures was uninjured. The orbits were gorged with blood….

In the 19th century, forensic pathologists began using pictures and words to show how various conditions appear in the cadaver, and to teach students and colleagues new methods of analysis. Line drawings, half-tone photography, and chromolithography, which could render coloration, texture, and subtle shading, became increasingly common as improvements in print technology made detailed illustrations cheaper to produce.

The mass manufacture of guns in the 19th century led to an epidemic of gunshot wounds incurred in wars, violent crimes, suicides, and accidents. The study of gunshot wounds became an integral part of criminal investigation and forensic pathology.

Physicians and surgeons first gained practical knowledge of death and decomposition through handling and dissecting bodies obtained for anatomical study. Over the course of the 19th and 20th centuries, the study of the decomposed body and body parts—the effects of time, environment, and manner of death—became a vital part of forensic science.

Fauna of the cadaver and time of death

In the 19th century, medico-legal researchers began studying patterns of insect colonization of the cadaver. Entomology, the study of insects, became one of the forensic sciences. By identifying the particular stages that insects go through as they develop on a dead body, and the succession of different species, forensic investigators attempt to determine where a victim died and estimate the time elapsed since death. These adult specimens represent some of the different insect species that colonize a cadaver.

The body farm: studying the science of decay

The Forensic Anthropology Center, at the University of Tennessee, Knoxville, conducts research into the postmortem decomposition of the human body. At the Center scientists study how variations in temperature, exposure, humidity and other environmental conditions affect cadavers and body parts. Their research has helped improve investigators' ability to estimate time of death and to identify individuals from skeletal remains. The Center also maintains a collection of documented human skeletons and has developed software that uses data from thousands of skeletons. Statistics from the database give investigators baselines that help them estimate the race, sex, and stature of unidentified bodies.

Adult female blow flies arrive within minutes to lay eggs on a cadaver. Each deposits about 250 eggs in the natural openings of the body and open wounds. The eggs hatch into first-stage maggots within 24 hours. These feed and then molt into second-stage maggots, which feed for several hours, and then molt into third-stage maggots. Masses of third-stage maggots may produce heat, which can raise the temperature around them more than 10° C. After more feeding, the third-stage maggots move away from the body and metamorphize into adult flies.

On September 21, 1986, the decomposing body of a 26-year-old woman was found inside a foul-smelling carpet near I-95 in Greenwich, Connecticut. Blow fly larvae were feeding on, and moving in and around, the body. Pale and dark brown blow fly puparia were recovered, along with 4,000 larvae, for laboratory study.

An autopsy revealed that the victim, Sylvia Hunt, had been stabbed 15 times. Forensic entomologist William Krinsky determined from climate and insect evidence that blow flies had deposited eggs on the corpse seven days earlier. The carpet pattern matched one in the room occupied by a suspect. The insect and carpet evidence helped convict him of first-degree murder.