Forensic medicine has been around for years, and is the least difficult area of scientific evidence (in terms of admissibility) because of a rather close relationship that exists between law and medicine. Pathology is the branch of medicine associated with the study of structural changes caused by disease or injury.
Forensic pathology simply adds the word "unnatural" or "suspicious" in front of the phrase 'disease or injury'. There are actually two branches of pathology: anatomic — which deals with structural alterations of the human body and clinical — which deals with laboratory examination of samples removed from the body.
Most forensic pathologists are experts in both branches. To become a forensic pathologist you must spend at least two years as an intern after graduation from medical school. An additional year of study is expected to prepare for passing the board exam with the American Board of Pathology. Such experts are certified at: establishing cause of death, estimating the time of death, inferring the type of weapon used, distinguishing homicide from suicide, establishing the identity of the deceased, determining the additive effect of trauma or pre-existing conditions.
Under the coroner system, the coroner is usually an elected official and need not even be a medical doctor, although they should have had at least some medical training. In Texas, for example, the Justice of the Peace is also usually the coroner (who calls inquests and orders lab tests).
Coroners are not exempt from civil liability for acts of negligence; medical examiners are. Medical examiners operate out of centralized offices at the state capital, or else they are part of an inter-county, regional arrangement. They are frequently vested with both law enforcement powers (to hire their own homicide investigators) and quasi-judicial powers (to call inquests and take sworn testimony).
The purpose of an autopsy is to observe and make a permanent legal record as soon as possible of the gross and minute anatomical peculiarities of a recently discovered dead body. Autopsies are typically done at a local hospital or at the county morgue, although some are done in private offices or in funeral parlors.
Anatomic examination may be sufficient to establish cause of death if the forensic pathologist has access to other information (such as surrounding circumstances; life history, psychiatric data, and other pertinent patient information).
Forensic pathologists also sometimes engage in "psychological autopsies", although these are not all that readily accepted by the legal system. Clinical, or microscopic, examination of organ parts is often necessary to further bolster the forensic pathologist's conclusions, although such examination would be impossible in an exhumation case (or where the family opposed it) since embalming usually thwarts microscopic lab testing.
Forensic pathologists almost always order X-ray examination whenever a firearm is involved. X-rays are also sometimes useful in stab wound and child abuse cases. The examination of organ parts from the body is useful in toxicology cases as well as anytime alcohol or drugs are suspected.
The inspection of stomach contents is part of every postmortem exam since it may provide information as to cause of death as well as time of death. Clinical examination also tends to confirm hunches about age, race, sex, height, weight, and general health condition in cases of unidentified remains.
The "manner of death" records whether the forensic pathologist thinks the death is a suicide, a homicide, accidental, natural, or unknown. The general rule is that manner equals mechanism plus immediate cause, but there are other general rules also. If the mechanism is undetermined, the death must be ruled as "unknown manner".
This occurs in some poisoning cases and other strange phenomenon (like spontaneous combustion). If the immediate cause simply aggravated a significant pre-existing condition (contributing cause), the death must be ruled "natural". Most traffic fatalities are ruled "accidental". All suicides are ruled as "homicides" if another person (other than decedent) is involved in the immediate cause of death.