Pathology is the investigation of death and disease. It emerged as a discipline from the mid-nineteenth century with the development of the microscope. Physicians began to see that the microscopic examination of tissue was relevant to the study of disease and had practical application in diagnosis and research. Two branches of pathology emerged; anatomic pathology involved the study of cells, tissues, and organs, while clinical pathology covered the study of body fluids such as blood and urine. The discipline of forensic pathology developed during the twentieth century, and is the application of pathology to the investigation of crime, particularly when injury or death have occurred.
The medical examiner (ME) is a key person in a forensic investigation. He or she is charged with looking into any suspicious death reported to them, be it a homicide, suicide, accident, or in any other way suspicious. To this end, their work involves specific tasks, chief of which is the determination of the cause and manner of the death through performing an autopsy . The ME also takes control of the analysis of evidence , works with the police investigating the scene of the crime, and presents evidence in court. Ideally and increasingly, the ME is a forensic pathologist. In practice, they must merely be medically qualified and may not even be a pathologist. In such cases, they may well contract out some of their duties, such as carrying out the autopsy, to a forensic pathologist elsewhere.
Becoming qualified as a forensic pathologist involves a lengthy course of study. After completing an undergraduate degree, the individual completes four years of medical school (in the United States; course lengths elsewhere may differ). Then, postgraduate training in pathology, which is done in a teaching hospital, takes at least four years more. After that, a further year's training is needed to become a forensic pathologist, and this is usually done in an ME's office, to get the necessary experience. The forensic pathologist can then take an exam to become board certified, which means he or she is finally qualified to assume the job of a medical examiner. Given the strong legal content of the ME's work, some forensic pathologists may also have some training in the law, or even a law degree.
The work of the forensic pathologist is quite varied. They will, like any other physician, often be involved in reviewing a patient's medical history. Many of the apparently suspicious deaths reported to the ME are actually from natural causes and the pathologist must be as aware of common diseases as of the methods used for homicide and suicide. If it appears as if a crime has been committed, then witness statements will be reviewed and, ideally, the scene of crime visited. Evidence of many types must be considered, from bloodstains and DNA , to toxicological analysis of blood and urine. All of this will help the medical examiner to determine the cause and manner of death.
Perhaps the most important part of the forensic pathologist's job is to carry out the autopsy, if one is required. This is done according to a standard procedure with notes and photographs taken at every stage. The forensic pathologist is also responsible for writing up a report on the investigation, which includes autopsy results and other findings, and presenting this to the court.
The forensic pathologist does not operate alone; he or she is part of an investigating team. In a large jurisdiction, the ME may have one or more assistants who may also be medically qualified. There are also posts for those who have degrees in science rather than medicine . A degree in biology, chemistry, or physics may secure a job as a technician, scientist, or laboratory manager in a facility where forensic pathology is done, particularly for candidates who have the appropriate post-graduate training in a branch of forensic science or experience in an appropriate laboratory.
Forensic pathology itself includes a number of specialties, including toxicology , serology , odontology , anthropology , and taphonomy . Laboratories, both governmental and private, devoted to each discipline will have openings for those qualified in medicine or science. A forensic pathologist needs to undertake further training to specialize in any of these disciplines. Toxicology involves the analysis of body fluids and tissues for poisons or drugs of abuse. There are two kinds of tests, a screen, which determines whether the drug is present, and a confirmatory test, which determines the amount of drug present. The two main applications of toxicology testing are in autopsy and in workplace drug testing, including sports testing . Work in the toxicology laboratory involves chemical analyses using techniques such as thin layer chromatography , gas chromatography , and ultraviolet spectroscopy . Technicians may be qualified in chemistry and chemical analysis. The pathology side involves determining the contribution that an individual drug may have made to a death. Drug overdose is involved in many deaths, but it can be challenging to work out whether such a death has been a suicide or an accident. Homicide by poisoning is rare nowadays, thanks, at least in part, to developments in toxicological analysis that make it easy to detect the most common poisons in human tissues.
Forensic serology is the study of blood and other body fluids. The work requires clinical pathology technicians to type blood that can incriminate or eliminate a suspect. Analysis of other body fluids, like semen , can help in the investigation of serious crimes such as rape. Body fluids, including saliva , can also be used to extract DNA, the ultimate form of individualizing evidence. The analysis of DNA and the interpretation of results is a specialized task, even though much of the instrumentation is automated these days. DNA technicians are expected to have training in molecular biology techniques.
DNA analysis is rapidly becoming the "gold standard" for identifying an individual. Dental records can be very useful in the identification of skeletal remains, one of the main uses of forensic odontology, or the application of dentistry to the investigation of crime. The other major application of forensic odontology is the analysis of bite marks left behind at the scene of a crime. Dental technicians may create casts of impressions of bite evidence; the interpretation of dental evidence is a specialist task involving comparison between dental records or impressions and the evidence. Even if only a few teeth are available with a set of human remains or if a bite mark is incomplete, the forensic odontologist can still offer an opinion as to the age and habits of that person, which can be set into context with other identifying information.
Like teeth, bones are enduring and their forensic analysis can often be used to make an identification. Forensic anthropology is the study of human skeletal remains to estimate, first of all, the age, sex, and race of the deceased. The anthropologist may also use toxicological and DNA analysis if these can be obtained from the remains. If a skull is available, identification can sometimes be made by comparing it with x rays obtained antemortem (before death). The forensic anthropologist needs a depth of knowledge to be able to estimate the age of bones (they may be so old as to be of little forensic significance), and whether they are indeed human.
The forensic pathologist deals with a "fresh" body, the anthropologist with bones. The study of the in-between stage, the decomposing body, is the realm of the forensic taphonomist. A human body undergoes specific changes after death. The rate of these changes, however, depends very much on the individual and the environment. Evaluation of these changes may help establish the all-important time of death .
Any pathologist working in the above disciplines may be called in as an expert witness to help resolve cases where the facts are unclear or in need of some explanation. A pathologist can help with the difficult question of cause of death when a body is recovered from water or how long it may have been in a shallow grave.
Being an expert witness is not a profession in its own right and a pathologist who carries out this work does not need to have special legal qualification. The expert witness is created and recognized as such by the judge and the court; he or she will usually have undergone training in court procedures so they can present their evidence to the best of their ability to help the judge and jury come to their decision.
Either the prosecution or the defense may call in a forensic pathologist as an expert witness. He or she is expected to look at the evidence relevant to their discipline, whether it is skeletal remains or analyses of body fluids, and put it in the context of the whole case. They will produce a report that can be taken up to the witness stand. First of all, the party who engaged the expert witness will ask questions that prove their identity, qualifications, experience, and background to the court. Then they will ask questions that generally take the court through the expert witness's report.
The expert witness can expect to be cross-examined by the opposing counsel who will ask questions as to the reliability of the evidence and the expert's conclusions. Many pathologists are experts in their subject, but it takes special skill and training to defend one's findings in public while still remaining objective and impartial.
The expert witness is the only one in court who is allowed to give opinion as well as facts. This is because the court has confidence in the facts and knowledge on which the opinion is based. Thus, the forensic anthropologist is allowed to say, for example, "I believe these bones are only about two years old and the cause of death was probably a blow to the head."
see also Expert witnesses; Forensic science.