Overview

Introduction

The purpose of death investigation is usually to answer the following questions: Who died, where, when, why and how? Thus the question of the cause, manner and mechanisms of death (the why and the how) is of central importance for every forensic practitioner. This introductory article aims to briefly present, mainly from an epidemiological point of view, the major causes of death encountered in developed countries. Deaths of particular medico-legal relevance, e.g. homicides and suicides are more widely developed in other articles.
According to their etiology and judicial relevance, deaths may be classified as follows:
• Natural deaths comprise all deaths presumed or certified of medical original, occurring under non-suspicious circumstances. They usually concern people displaying a history of acute or chronic, life-threatening disease and dying in hospitals, other health facilities or at home, under the care of practitioners able to assess the cause of death.
• Violent deaths are all deaths not caused by the spontaneous, terminal evolution of a pathological process, but resulting from an external (and usually sudden) action or force. They include homicides, suicides and accidents.
• Suspicious or unattended deaths are deaths initially of dubious origin that require further forensic investigations to be ruled as natural or violent (e.g. young adults found dead at home, or sudden death at a workplace), or deaths of obvious natural or violent origin but which occurred under suspicious circumstances (e.g. ischemic heart disease in a context of medical mishap, or firearm death without prior indication on the suicidal or criminal origin).
Overall most deaths occur from natural causes (Table 1). The three main causes in all developed countries are diseases of the heart, malignant neoplasms and cerebrovascular diseases. There are, however, outstanding differences in the distribution of the leading causes of death according to the age group.
• Infant mortality (i.e. all deaths of subjects < 1 year old) is mainly linked to factors originating in pregnancy or the perinatal period: congenital anomalies, disorders related to short gestation and/or low birth weight, sudden infant death syndrome, respiratory distress syndrome, infections specific to the perinatal period.
• Children, teens and young adults are disproportionately affected by deaths of violent origin. As shown in Table 1, the three leading causes of death in young Americans aged 15-24 years are accidents, homicides and suicide.
• Adults over 45 years and the elderly are more concerned by deaths of natural origin. Over half of all deaths recorded in this age group are due to heart failure or malignant neoplasms.
Natural deaths are frequently considered of limited forensic interest. This is, however, not always the case, as some of them may raise social or legal problems (deaths of unknown individuals, deaths at work, deaths in legal custody, deaths involving medical liability, cause of death contested by insurers, sudden infant deaths) that can be solved only by forensic examination. In addition the definition of what is relevant to forensic investigation differs strongly depending on the local judicial system. In many European countries (e.g. France, Italy, Spain) postmortem examination is ordered only for certain limited categories of death and in the context of a judicial inquiry, primarily to establish whether or not there has been any criminality or possible negligence leading to the death; once these possibilities have been ruled out, it does not remain mandatory to establish the precise cause of death. In other countries (e.g. the medical examiner system in the USA) postmortem investigations are carried out on a much broader range of death situations and the forensic specialists are compelled to indicate the precise cause and manner of death even if obviously natural and without any legal relevance. In addition to individual case investigation and management, this systematic approach has an epidemiological interest since it allows the collection of accurate data of prime usefulness for the establishment of population statistics.

Table 1 Leading causes of death in the USA, 1996 (death rates per 100000 population in specified group)

Accidents

An accident is an unintentional event, due to the sudden and unexpected action of an external cause, resulting in physical damage to persons. In the USA accidents are the fifth leading cause of death (all ages) and the first cause for people aged 1-24 years. In 1995 they were responsible for 35.6%, 41.2% and 40.4% of all deaths recorded in persons aged 1-4, 514 and 15-24, respectively (death rates 14.5, 9.3 and 38.5 per 100 000 population, respectively); the overall accidental death rate was 35.5.
Accidents should be subdivided into two main categories: traffic accidents (or motor vehicle accidents) and nontraffic accidents. Traffic accidents are the main cause of accidental death in all developed countries. In 1993 90 523 Americans were killed in accidents and of these, 40 899 died in road accidents (45.2%). The prevalence of accidental deaths due to nonroad transport (water, air, railway) is very low compared with that of traffic accidents. Falls were the second cause of accidental death (13141 deaths, 14.5%); death rates by age group show an increase of fall-related fatalities with advancing age, many of these death occurring in elderly persons who die of the complications following a fall. Other kinds of nontraffic accidents include (percentages referring to the 1993 US data):
• Accidental poisonings by drugs and medicines (including overdoses by drugs of ab use): 8.2%
• Accidents caused by fires and flames: 4.3%
• Accidental drowning: 4.2%
• Accidental inhalation and ingestion of objects:3.5%
• Complications due to medical procedures: 2.9%
• Accidents involving firearms (handguns and other): 1.7%
• Accidental poisonings due to gases and vapors:0.7%
According to the 1995 report of the North Carolina Office of the Chief Medical Examiner, of 2682 deaths ruled accidental in manner, 1557 (58.1%) involved motor vehicles. The nonmotor vehicle accidents distributed as follows: falls 30%, poisonings (alcohol + other) 16%, fires 13%, drowning 13%, exposure 2%, all other 26%.
Traffic accident death rates are generally lower in European countries, compared with the United States. In France 124 387 road accidents with physical damage were reported in 1998, responsible for 8437 deaths and 168 535 injured (mortality and morbidity rates 14.5 and 289.3 per 100 000 population, respectively).

Suicides

Suicide statistics remain approximate, but in most countries they depict a major problem of public health. Depending on sources (WHO, national data networks, associations), the estimated number of people dying by suicide in the world is between 440 000 and 800 000 per annum. According to the National Center for Health Statistics (NCHS), there were 30 903 deaths by suicide in the USA in 1996, representing 1.3% of total deaths (suicide rate 11.6 per 100 000). Overall, suicide is the ninth leading cause of death for Americans. There are about 775 000 annual attempts at suicide in the USA, i.e. roughly 25 attempts for every completion. These data are the average among industrialized nations. Among developed countries, Hungary has the highest suicide rates. France ranks fourth (about 12 500 deaths recorded in 1997); there are at least 90 000-115 000 attempts per year, i.e. a rate of 200-250 per 100 000 French residents aged over 15. In many European countries, there are more deaths by suicide than by road accidents (also due to the lower prevalence of traffic deaths). Suicide rates are generally much lower in developing countries.
In all developed countries, there are marked discrepancies between population groups, as follows.
• Gender: more women than men have a history of attempted suicide (at a ratio of 2:1 to 5:1), whereas more men than women die by suicide (at a ratio of 3:1 to 5:1) as they frequently choose more radical methods. In the USA, male and female suicide rates (1996) are 19.3 and 4.4 per 100 000, respectively.
• Age: suicide rates generally increase with age. US residents over age 65 have a suicide rate of 17.3 per 100 000 (1996) and those over age 85 of 20.2 (highest rate of any age group), whereas young people aged 15-24 years have a rate of 12.1. In France, suicide rates remain relatively level for people 25-65 (around 40 per 100 000), then increase sharply for the elderly (91 per 100 000 for the 75-84). However, since much fewer young persons die of health-related causes, suicide represents everywhere a leading cause of death among adolescents (third in the U.S.A.).
• Ethnic origin: Whites display higher suicide rates than all other ethnic groups.
• Place of residence: in America, the state with the highest suicide rate in 1996 was Nevada (20.9 per 100 000), and the lowest was the District of Columbia (6.4 per 100 000).
Typical risk factors of suicide attempts include mental disorders, substance abuse, history of family violence, adverse life events such as loss of job or incarceration (suicide rates in jail exceed those of the general population by 10-30 times), exposure to the suicidal behavior of others, prior suicide attempts, firearms or pharmaceuticals available at home.

Suicide methods

Among industrialized nations most suicide attempts (> 70-80%) involve drug overdoses, mainly with psychotropics. However, the great majority of such attempts remain unsuccessful, because today’s pharmaceuticals have become much safer: fatalities involving benzodiazepines, or selective serotonin reuptake inhibitors are exceptional, which previously was not the case with barbiturates or first-generation tricyclic antidepressants.
The three main methods observed in completed suicides are firearms, hanging and drug overdose (including pharmaceuticals and drugs of abuse). Guns are by far the most common method used by both men and women in the USA, accounting for 60.3% of all suicides in 1994, and 58.8% in 1996.
This method is less prominent in Europe due to more restrictive regulations on firearms. Depending on the country, either hanging or firearms rank first in males, close to each other, followed by poisoning; females preferentially choose poisoning, jumping from heights or drowning. Hanging is the technique of choice for captive persons (patients of psychiatric wards, prison inmates) who do not have access to more sophisticated methods. In France, 98% of suicide deaths in prison are by hanging. In developing countries the most popular methods are hanging and poisoning (more harmful than in Europe or North America because it frequently involves highly toxic industrial or agricultural substances).
A second group of methods are less usual but not exceptional, as each accounts for 5-15% of suicides in developed countries: gas poisonings (mainly carbon monoxide), drowning, jumping from heights. All other methods may be held exceptional, none of them exceeding 2% of suicide deaths; they include:
• burning
• electrocution
• suicide by sharp force: wrist cutting (frequent in suicide attempts especially in females or adolescents, but almost never successful), arteriotomy, stabbing at throat or trunk, self-mutilation
• use of motor vehicles
• asphyxic methods other than hanging: strangulation, suffocation

Homicides

Homicide may be defined as the willful killing of one human being by another. Some discrepancies, however, exist between statistics originating from different sources, depending on whether they include (or not) in the definition: (1) deaths caused by reprehensible negligence (nonpardonable negligent manslaughter); (2) justifiable homicides (the killing of a felon by a police officer in the line of duty, or by a private citizen, e.g. in self-defense situations).
A total of 18 211 US residents were murdered in 1997, a rate of 6.8 per 100 000 population. Almost level since 1950 (4.6 per 100 000), the homicide rate doubled from the mid 1960s (4.9 in 1964) and peaked at 10.2 in 1980. It subsequently decreased (7.9 in 1985), then rose again to a peak of 9.8 in 1991. Since then the homicide rate has declined continuously to levels last seen in the late 1960s. In spite of this relative improvement, the homicide rates observed in the United States remain at the highest level among industrialized countries, due to legal (regulations on firearms) and sociological reasons. For instance there were ‘only’ 581 homicides in Canada in 1997, a homicide rate of 1.92 per 100 000, i.e. less than one-third of that of the United States but still higher than in most European countries (France 1.66, England and Wales 1.00). The recent decrease of homicide rates appears to be general. The 1997 Canadian data represent a 9% decrease from 1996 and the lowest rate since 1969. In France 963 persons were murdered in 1997, a 17.8% decrease from the previous year.

Characteristics of victims and offenders

Homicide statistics recorded in various industrialized nations highlight some characteristics of victims and offenders that may be considered as roughly constant.
Age Homicide primarily concerns young adults. In the United States the involvement of teens and young adults as both victims and offenders increased dramatically in the late 1980s whereas rates for older age groups declined. Since 1986 the highest homicide victimization rates concern people aged 18-24 years (+16% annually during 1986-1991), whereas they were previously observed among the 25-34 years olds; homicide offending rates followed a similar pattern. This is confirmed by a continuous decrease of the average age of both victims and perpetrators: the average age of victims fell from 35.2 years in 1976 to 31.7 years in 1997, and that of offenders from 30.8 to 27.7 years. Similarly, Canadian residents aged 1829 years had the highest homicide rate as victims in 1997 (3.39 per 100 000), whereas the elderly aged 60 years and older had a rate of 1.46; the lowest rate, 1.16, was for children and young people aged 18 and under.
Gender Men are most often the victims and the perpetrators in homicides. Homicide is the tenth leading cause of death of men in the United States. In 1997, male US residents were 3.6 times more likely than women to be murdered, and nine times more likely to be the perpetrator of a murder. The combination ‘male offender/male victim’ represented 67.9% of all homicides reported (male offender/ female victim: 22.0%; female offender/male victim: 7.8%; female offender/female victim: 2.3%). These data are in accordance with a compilation of US homicide statistics from 1976 to 1994, which showed that 76% of the murder victims were male, as were 86% of the known murderers. However, when a sexual assault was associated with the homicide, 95% of the offenders were male and 82% of the victims were female.
Ethnic origin There are marked differences between American Blacks and Whites for both homicide victimization rates and homicide offending rates. Blacks are seven times more likely than Whites to be murdered, and eight times more likely to commit homicide. Most murders are intraracial; the compilation of data from 1976 to 1997 indicates that 85% of white victims were killed by Whites, and 94% of black victims by Blacks. It is difficult to compare these results with those of other countries, as many national regulations (especially in Europe) prohibit the computation of racial origin in population studies.
Relationships between victim and offender Most homicide victims know their killers. In Canada, only 13% of all victims were killed by a stranger in 1997. Two subcategories are of particular interest in the context of intrafamilial violence: spousal homicide, and infant and child homicide.
Spousal homicide Women are far more likely than men to be killed by their spouse. Over the past decade, three times more women than men have been killed by their spouse in Canada; in 1996, 78% of all spousal homicide victims were female and 22% were male. Women are also far more likely to be killed by their spouse than by a stranger; in 1997, 61 women were murdered by a current or exspouse in Canada, whereas 12 were killed by a stranger; during the period 1974-1992, a married woman was nine times more likely to be murdered by her husband than by a stranger. Some situations are frequent in families where the man shot and killed his wife, thus may be held as risk factors for such events: violent disputes, alcohol abuse, criminal record of the husband, financial difficulties, illegal possession of firearm, separation or divorce in the process or completed, large age difference between spouses.
Infant and child homicide In 1997 a total of 623 children under the age of 5 years were murdered in the United States. The race-adjusted homicide rates were 2.3 and 8.7 per 100 000 for white and black children, respectively. Most of the children killed were male. The majority of these homicides were committed by a parent: 27% by mothers, 27% by fathers, 6% by other relatives, 24% by acquaintances and only 3% by a stranger. In a similar way, 53 children under 12 (including 18 infants) were murdered in Canada in 1997, three quarters of them by a family member.
A significant proportion of homicides, especially those involving relatives, are followed by the suicide of the offenders. According to a report from the Canadian Department of Justice, 70% of men who shot and killed their wife in 1989 and 1990 subsequently turned the gun on themselves.

Homicide methods

The worldwide three most popular methods used for killing somebody are shooting, stabbing and beating. In the United States homicides are most often committed with firearms (roughly seven out of ten murders in all statistics), far below stabbing then blunt force. Of 18 211 people murdered in 1997, 9796 were killed using a handgun (53.8%), 2601 using another kind of gun (14.3%), 2355 using a knife (12.9%), 822 using blunt force (4.5%), and 2637 using other methods. Given an attack, guns are more likely to result in serious injury and death than if any other weapon is used: firearm attacks are about three times more likely to be lethal than knife attacks, and still many times more likely than attacks involving other methods. Firearm-associated family and intimate assaults are 12 times more likely to result in death than nonfirearm incidents.
In all developed countries but the United States, the prominence of gun attacks in homicides is far less pronounced. During the past decade there has been an average of 1300 gun-related deaths per year in Canada and of these, homicides accounted for only about 15%, suicides 80% and accidents 5%. Over this period firearm homicides have remained relatively constant at about one-third of total homicides; for instance, of 633 homicides reported in 1996, 211 (33%) involved firearms. From 1985 to 1995 inclusive, the average firearm homicide rate per 100 000 population was 0.7 in Canada, compared to 5.6 in the United States.
The fourth homicide method by order of frequency is mechanical asphyxiation performed by strangulation or suffocation. Since this method generally requires a large strength difference between offender and victim, it is particularly frequent in the following offender/victim combinations: male adult/female adult, male adult/child or infant, female adult/child or infant. All other homicide methods may be considered rare to exceptional, including burning, drowning, intentional poisoning by solids, liquids or gases, electrocution, precipitation from heights and starvation.