The word ‘forensic’ derives from the Latin forum meaning ‘a market place’: in Roman times, the forum was where people conducted business transactions and some legal proceedings. For many years, the term ‘forensic’ had a restricted definition and denoted a legal investigation. However, nowadays it applies to any detailed analysis of past events, i.e. when one looks for evidence. For example, tracing the source of a pollution incident is now a ‘forensic environmental analysis’, determining past planetary configurations is ‘forensic astronomy’, whilst ‘forensic musicology’ refers to the comparison of two pieces of music in cases of alleged copyright infringement. For the purposes of this book, ‘forensic biology’ is defined broadly as ‘the application of biological sciences to legal investigations’ and therefore covers human anatomy and physiology, viruses to vertebrates and topics from murder to the trade in protected plant species.

Although forensic medicine and forensic science only became specialised areas of study within the last 200 or so years, their origins are traceable back to the earliest civilisations. The first person in recorded history to have medico‐legal responsibilities was Imhotep, Grand Vizier, Chief Justice, architect and personal physician to the Egyptian pharaoh Zozer (or Djoser). Zozer reigned from 2668 to 2649 BC and charged Imhotep with investigating deaths occurring under suspicious circumstances. The Sumerian king Ur‐Nammu (ca 2060 BC) began the first codification of laws with the eponymous ‘Ur‐Nammu Code’, in which penalties of various crimes were stipulated. The first record of a murder trial appears on clay tablets inscribed in 1850 BC at the Babylonian city of Nippur.

In England, the office of coroner dates back to the era of Alfred the Great (871–899), although his precise functions at this time remain uncertain. It was during the reign of Richard I (1189–1199) that the coroner became an established figure in the legal system. The early coroners had widespread powers and responsibilities that included the investigation of crimes ranging from burglary to murder and suspicious death. The body of anyone dying unexpectedly had to be kept for inspection by the coroner, even if the circumstances were not suspicious. Failure to do so meant that those responsible for the body were fined, even though it might have putrefied and created a noisome stench by the time he arrived. It was therefore common practice for unwanted bodies to be dragged away at night to become another village's problem. The coroner's responsibilities changed considerably over the centuries, but up until 1980, he was required to view the body of anyone dying in suspicious circumstances.

Although the coroner was required to observe the corpse, he did not undertake an autopsy. In England and other European countries, dissection of the human body was considered sinful and was banned or permitted only in exceptional circumstances until the nineteenth century. Most Christians believed that after a person died, their body had to be buried ‘whole’. If it was not, the chances of material resurrection on Judgement Day were slight. The first authorised human dissections took place in 1240, when the Holy Roman Emperor Frederick II decreed that a corpse could be dissected at the University of Naples every five years to provide teaching material for medical students. Subsequently, other countries followed suit, albeit slowly. In 1540, King Henry VIII became the first English monarch to legislate for the provision of human dissections by permitting the Company of Barber Surgeons to examine the corpses of four dead criminals per annum. In 1663, King James II increased this figure to six per annum. Subsequently, after passing the death sentence, judges had the option of decreeing the body of the convict to be buried (albeit without ceremony), or exposed on a gibbet or dissected. Nevertheless, the lack of bodies and an eager market among medical colleges created the trade of body snatching. Body snatchers usually left behind the coffin and the burial shroud, because taking these counted as a serious criminal offence – which was potentially punishable by hanging. Removing a body from its grave was merely a ‘misdemeanour’. The modern‐day equivalent is the Internet market in human bones of uncertain provenance. A notorious case arose in 2004 when the body of the eminent journalist Alistair Cooke was plundered whilst ‘resting’ in a funeral parlour in New York. Despite being 95 years old at the time of his death and suffering from cancer, his arms, legs, and pelvis were surreptitiously removed. These were then sold to a tissue processing company for use in surgery or as dental filler. The trade in human bones is legal provided the correct protocols are followed, but it is also highly lucrative and this tempts some people into criminal behaviour.

Although the ancient Greeks performed human dissections, Julius Caesar (102/100–44 BC) has the dubious distinction of being the first recorded murder victim in history to undergo an autopsy. After the assassination, the physician Antistius examined his body. He concluded that although Julius Caesar was stabbed 23 times, only the second of these blows, struck between the first and second ribs, was fatal. The first recorded post mortem to determine the cause of a suspicious death took place in Bologna in 1302. A local man called Azzolino collapsed and died suddenly after a meal and his body quickly became bloated whilst his skin turned olive and then black. Azzolino had many enemies and his family believed that he had been poisoned. A famous surgeon, Bartolomeo de Varignana, was called upon to determine the cause and he was permitted to undertake an autopsy. He concluded that Azzolino died because of an accumulation of blood in veins of the liver and that the death was therefore not suspicious. Although this case set a precedent, there are few records from the following centuries of autopsies to determine the cause of death in suspicious circumstances.

The first book on forensic medicine may have been written by the Chinese physician Hsu Chich‐Ts'si in the sixth century CE but this has since been lost. Subsequently, in 1247, the Chinese magistrate Sung Tz'u wrote a treatise entitled ‘Xi Yuan Ji Lu’ that is usually translated as ‘The Washing Away of Wrongs’, and this is generally accepted as the first forensic textbook. Sung Tz'u would also appear to be the first person to apply an understanding of biology to a criminal investigation. He relates how he identified the person guilty of a murder by observing the swarms of flies attracted to bloodstains on the man's sickle. In Europe, medical knowledge advanced slowly over the centuries and forensic medicine really only started to be identified as a separate branch of medicine in the 1700s (Chapenoire and Benezech 2003). The French physician Francois‐Emanuel Foderé (1764–1835) wrote a landmark 3‐volume publication in 1799 entitled Les lois éclairées par les sciences physiques: ou Traité de médecine‐légale et d'hygiène publique that is recognised as a major advancement in forensic medicine. In 1802, the first chair in Forensic Medicine in the UK was established at Edinburgh University and in 1821 John Gordon Smith wrote the first book on forensic medicine in the English language, entitled ‘The Principles of Forensic Medicine’.

Today, forensic medicine is a well‐established branch of the medical profession. Clinical forensic medicine deals with cases in which the subject is living (e.g. non‐accidental injuries, child abuse, rape), whilst forensic pathology deals with investigations into causes of death that might result in criminal proceedings (e.g. suspected homicide, fatal air accident). Pathology is the study of changes to tissues and organs caused by disease, trauma, toxins, and other harmful processes. Theoretically, any qualified medical doctor can perform an autopsy. However, in practise, at least in the UK, only those doctors who have received specialist training in post‐mortem pathology conduct autopsies.

The majority of deaths are not suspicious, so an autopsy is unlikely to take place. Indeed, even if a doctor requests an autopsy, the relatives of the dead person must give their permission. Some religious groups are opposed to autopsies and/or require a person to be buried within a short period of death so an autopsy may be refused. For example, many Muslims, orthodox Jews and some Christian denominations oppose autopsies. Some doctors are concerned about how few autopsies take place. This is because some estimates suggest that 20–30% of death certificates in the UK incorrectly state the cause of death. The errors are seldom owing to incompetence or a ‘cover‐up’, but result from the difficulty of diagnosing the cause of death without a detailed examination of the dead body.

There are rogue elements in all professions and the GP Dr Harold Shipman murdered over 200 mostly elderly patients over the course of many years. He did this through administering morphine overdoses and then falsifying the death certificates (Pounder 2003). Dr Shipman's victims suffered from a range of chronic ailments and because of their age and infirmities, nobody questioned the certificates he signed. He also falsified his computer patient records. It therefore appeared that the patient suffered from the condition that Dr Shipman claimed caused their death. He sometimes did this within hours of administering a fatal dose of morphine. Ultimately, suspicions were aroused and several of his victims who had been buried were disinterred and autopsied. The findings indicated that although they may have been infirm, they had not died because of disease. Their bodies did, however, contain significant amounts morphine. Providing the tissues do not decay too much, morphine residues are detectable for several years after death. Dr Shipman had therefore, surprisingly for a doctor, chosen one of the worst poisons in terms of leaving evidence behind. Dr Shipman was found guilty of murdering 15 of his victims in January 2000 and subsequently committed suicide whilst in prison.

In England and Wales, when a body is discovered in suspicious circumstances, the doctor issuing the death certificate or the police will inform the coroner. They can then request that an autopsy be performed regardless of the wishes of the relatives. In this case, the autopsy is undertaken by one of the doctors on the Home Office List of pathologists: as of 23 June 2017, there were 36 of them. Each of the Home Office Pathologists covers one of seven regions of England and Wales. The name is a bit of a misnomer because although the Home Office accredits them, the Home Office does not employ them. Scotland has its own laws and the Procurator Fiscal decides whether a death is suspicious and whether one or two pathologists should conduct the autopsy. The situation in Northern Ireland is slightly different again, with pathology services provided by The State Pathologist's department. Other countries have their own arrangements.

Animals and plants have always played a role in human affairs, quite literally in the case of pubic lice, and have been involved in legal wrangles ever since the first courts were convened. There is a long history of disputes over ownership, the destruction of crops and the stealing or killing of domestic animals. For example, Hammurabi, who reigned over Babylonia during 1792–1750 BC, codified many laws relating to property and injury that subsequently became the basis of Mosaic Law. Among these laws, it states that anyone stealing an animal belonging to a freedman must pay back 10‐fold, whilst if the animal belonged to the court or a god, then he had to pay back 30‐fold. Animals have also found themselves in the dock accused of various crimes. In the Middle Ages, several cases are recorded in which pigs, donkeys and other animals were executed by the public hangman following their trial for murder or sodomy. The judicial process was considered important, the animals were appointed a lawyer to defend them, and they were tried and punished like any human. In 1576, the hangman brought shame on the German town of Schweinfurt by publicly hanging a pig in the custody of the court before due process took place. He never worked in the town again and his behaviour gave rise to the term ‘Schweinfurter Sauhenker’ (Schweinfurt sow hangman) to describe a disreputable scoundrel (Evans 1906). Sadly, the phrase has now fallen out of fashion. Today, the owner of a dangerous animal is prosecuted when it wounds or kills someone, although it may still face the death penalty.

During the nineteenth century, a number of French workers made detailed observations on the sequence of invertebrate colonisation of human corpses in cemeteries, and attempts were made to use this knowledge to determine the time since death in murder investigations. Thereafter, invertebrates were used to provide evidence in a sporadic number of murder investigations, but it was not until the 1980s that their potential was widely recognised. Part of the reason for the slow development is the problem of carrying out research that can be applied to real case situations. Pigs, and in particular foetal pigs, are the forensic scientists' usual choice of corpse, although America has a ‘Body Farm’ in which dead humans can be observed decaying under a variety of ‘real life (death?) situations’ (Bass and Jefferson 2003). Leaving any animal to decay inevitably results in a bad smell and attracts flies – so it requires access to land far from human habitation. It also requires protecting the body from birds, dogs, and rats that would drag it away. Consequently, it is difficult both to obtain meaningful replicates and to leave the bodies in a ‘normal’ environment. Even more importantly, in EU countries, these types of experiments conflict with European Union Animal By Products Regulations, which require the bodies of dead farm and domestic animals to be disposed of appropriately to avoid the spread of disease – and leaving a dead pig to moulder on the ground clearly contravenes these.

The use of animals other than insects as forensic indicators has proceeded slowly and that of plant‐based evidence has been slower still. The first use of pollen analysis in a criminal trial appears to have taken place in 1959 (Erdtman 1969). Although not widely used in criminal trials since then, its potential is increasingly recognised. By contrast, the use of plants and other organisms in archaeological investigations has been routine for many years. Microbial evidence seldom features in criminal trials, although this is likely to change with the development of new methods of detection and concerns over bioterrorism.

The use of molecular biology in forensic science has expanded rapidly since the landmark Colin Pitchfork case in 1988, and it is now an accepted procedure for the identification of individuals. Indeed, the use of DNA in forensic science is in danger of becoming a victim of its own success. For example, some commentators have voiced concerns that juries (and lawyers) might consider that DNA evidence is mandatory for a successful prosecution and ignore all other sources of information. In addition, the latest DNA sequencing methods can now detect extremely small amounts of DNA. This means that there is an increased risk of detecting contaminating transfer DNA. In addition, new methods of analysing DNA are revealing information about us that is potentially valuable to law enforcement agencies but also poses privacy issues. On a more positive note, the techniques required to analyse non‐human DNA are advancing rapidly. This will lead to increasing use of evidence from animals and plants in legal proceedings.

A major obstacle to the use of biological evidence in English trials is the nature of the legal system. In a criminal prosecution case, the court must be sure ‘beyond all reasonable doubt’ before it can return a guilty verdict. The court therefore requires a level of certainty that science rarely provides. Indeed, science is based upon hypotheses and a scientific hypothesis is one that can be proved wrong – if one can find the evidence. Organisms are affected by numerous internal and external factors and therefore the evidence based upon them usually has to have qualifications attached to it. For example, suppose the pollen profile found on mud attached to a suspect's shoe was similar to that found at the site of a crime. This suggests a possible association but it would be impossible to state beyond reasonable doubt that no other sites have similar profiles – unlikely perhaps, but not beyond doubt. Lawyers are, quite correctly, experts at exploiting the weaknesses of biological evidence. In particular, it is seldom possible for one to state there is no alternative explanation for the findings or an event would never happen. Within civil courts, biological evidence has greater potential, since here the ‘burden of proof’ is based upon ‘the balance of probabilities’.

Although all biological evidence has its limitations, it is often useful in answering many of the questions that arise whenever a body is found under suspicious circumstances. The first question is, of course, are the remains human? This might be obvious if the body is whole and fresh or even if there is just a skull but sometimes there may be no more than a single bone or some old bloodstains. Assuming that the remains are human, biological evidence can also help to answer the subsequent questions (Table I.1).

Similar questions arise in wildlife crime (e.g. killing of/trade in protected species), neglect of humans and domestic animals, mis‐selling of animal products, and food contamination. This book intends to demonstrate how an understanding of biology can answer all these questions. It is designed for undergraduates who may have a limited background in biology and not the practicing forensic scientist. I have therefore kept the terminology simple, whilst still explaining how an understanding of biological characteristics provides evidence. Descriptions of potential sources of biological evidence and tests continue to grow at a bewildering rate. Therefore, it is essential to distinguish between approaches that will be useful in the real world and those that will never proceed further than the laboratory pilot study. To be truly useful any test/source of evidence must be accurate, simple, affordable, and deliver results within an acceptable period (Table I.2). With such a large subject base, it is impossible to cover all topics in depth and readers wishing to identify a maggot or undertake PCR analysis should consult one of the more advanced specialist texts or review articles mentioned at the start of each chapter. Where information would not otherwise be easily accessible to undergraduate students, I make use of web‐based material, although the usual caveats apply to such sources.

This is the third edition of Essential Forensic Biology and although the basic structure is similar, all the chapters have been re‐written, updated, and include many new illustrations. Some of the chapters in the second edition are now divided into two, in order to provide greater focus and in‐depth coverage of topics. There is also a new chapter on Wildlife Forensics. This is in recognition of the scale of the problem and the consequences it is having on both the environment and human societies. The illegal trade in wildlife is a global problem and often involves other illegal activities and organised criminal gangs. There is also an expanded Companion Website. This includes multiple choice questions (and answers) and short answer questions associated with each chapter. In addition, there are interpretative questions that require the reader to utilise information gained from several chapters. The website now includes numerous photographs that could not be included in the book without increasing its size and cost. I provide some ideas for project work that do not require access to complex laboratory facilities. Because the usefulness of biological material as forensic evidence depends on a thorough understanding of basic biological processes and the factors that affect them, there is plenty of scope for simple projects based upon identifying species composition or that measure growth rates. Obviously, for the majority of student projects, cost, time, and facilities are serious constraints. Although DNA analysis is extremely important in many aspects of forensic biology, it can be expensive and requires specialist equipment. Similarly, the opportunities to work with human tissues or suitably sized dead pigs may not exist. However, one can undertake worthwhile work using the bodies of laboratory rats and mice or meat and bones bought from a butcher as substitute corpses with plants and invertebrates as sources of evidence.

At the start of each chapter, I list a series of ‘objectives’ to illustrate the material covered. These take the form of examination essay questions, so that the reader might use them as part of a self‐assessment revision exercise. I divide the book into a series of conventional chapters but because topics are inter‐related, the reader will find certain subjects picked up, put down, and then returned to later. This is also a good way of learning, since it is better to take in bite‐sized chunks of information and return to them frequently, rather than attempt to grasp all aspects of a topic in a single sitting. The book begins with a discussion of how the human body decays and how one discovers and recovers a dead body. There is then an in‐depth consideration of how one conducts DNA and RNA analysis and how this contributes to forensic biology. This area of science is advancing at an incredible speed, but in the process of providing a wealth of information that can help solve crimes, it is also throwing up serious practical and ethical issues. The book then deals with body tissues and fluids as forensic indicators. We then consider how wound analysis can help establish whether a suspicious death was a result of an accident, suicide, or homicide. Film and TV depictions of forensic pathology often suggest a degree of certainty when diagnosing the cause of death that is not always possible. This chapter emphasises the importance of proceeding cautiously and keeping an open mind. There is then a consideration of the animal kingdom as forensic indicators. This begins with the invertebrates. These are used primarily to determine the minimum time since death, although their importance in other scenarios is also considered. We then deal with the vertebrates and, as mentioned previously, there is now a new chapter on wildlife forensics.

The chapter on plants as forensic indicators is now longer because until recently this source of forensic evidence was often overlooked. In addition, there is now more information on plant poisons, such as ricin, because of the concern about their use by terrorists and hostile governments targeting unwelcome critics. There is also more information on the illegal trade in plants, because it is equally important (and profitable) as illegal animal trafficking but seldom receives attention in the popular press. The final chapter on microbes and viruses now includes a detailed consideration of the prospects of microbiomes as forensic indicators. To its supporters, microbiome analysis offers the prospects of revolutionising our understanding of many disease processes and the prospects of new therapeutic approaches. As a spin‐off from this, microbiome analysis is increasingly proposed as a new means of answering forensic questions such as the time since death, individual identity, and geographical origin. This chapter considers the strengths of these claims. There is also new information on the transmission of a disease as a criminal act and the use of microbes and viruses in bioterrorism.