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Homicidal poisoning: the silent offense.

"Poisoning, of course, differs considerably from many other crimes, frequently committed in uncontrolled passion and in the heat of the moment. The innate character of the crime of homicidal poisoning demands subterfuge, cunning, and, what is equally important, usually a period of careful planning, and also not infrequently the repetition of the act of administering poison.... Its characteristic being one of premeditation, it is a method of murder, which, therefore, cannot be the subject of extenuation as some other forms of killing can." (1)


Given such a description, the crime of homicidal poisoning would seem a rich arena for research. Surprisingly, however, other than a few published reviews of some famous historical poisoning cases, the authors found little written material on the characteristics of poisoners and their victims. (2) A further probe of the international forensic literature also failed to reveal any previously published epidemiological studies dealing with criminal investigative analyses, or psychological "profiles," of the homicidal poisoner. Yet, the potential for toxic substances becoming weapons of mass destruction has increased dramatically in recent years. Therefore, the authors wondered if empirical data concerning homicidal poisoners and their victims would reveal relationships, patterns, and characteristics that could help law enforcement professionals. Building on the few empirically based studies that exist, they examined recently reported poisoning homicides to find out.


To conduct this research, the authors drew upon FBI Uniform Crime Reporting (UCR) supplementary homicide reports (SHR) of those incidents occurring in the United States over the last decade (1990-1999). Specifically, they examined these data to isolate homicides where a poisoning agent was reported as the cause of death. (3) The authors intentionally selected this time period to permit comparisons with an earlier work that reviewed similar data reported over the period of the previous decade (1980-1989). (4)


Traditionally, the UCR program has offered the criminal justice community a way to look for fluctuations in the level of crime and to provide statistics for varied research and planning purposes. From these data, the SHRs reveal much of what criminologists know empirically about the nature and scope of homicidal behavior in the United States.

For this study, 186,971 SHR murders in the United States that occurred during the 10-year period 1990-1999 were available for analysis. This volume of cases represented an 8 percent decline in reported murders compared with the 202,785 homicides recorded in the decade of the 1980s. From these cases, the authors extracted those homicides involving a chemical (nondrug) poison or a drug/narcotic that an offender had used for homicidal purposes. They excluded reports entailing asphyxiation/fumes because the data did not allow them to differentiate asphyxiation by smothering from those cases concerning chemical fumes (e.g., carbon monoxide).



Of the total 186,971 SHR reports in the United States for the period 1990-1999, 346, or 1.9 per 100,000 total homicides, were poisonings involving a single victim and a single offender or a single victim and an unknown number of offenders. (5) Compared with the 1980s when 292 similar homicidal poisonings were reported, the 1990s saw an increase of 18 percent of these crimes, which represented a 35 percent increase in the rate of these cases coming to the attention of law enforcement during these years.


The effective investigation of homicides generally, and poisoning cases in particular, often depends upon a number of factors, including such basic investigative data as victim demographics, possible offender characteristics, geographic and temporal features of the case, and any particular incident attributes that may assist law enforcement. The findings of this study, therefore, underscore the importance of cooperation between the medicolegal and law enforcement communities and serve as a foundation for the continued examination of behavioral attributes of homicidal poisoners.

Victim Demographics

The SHR data for the 1990s showed that victims of homicidal poisonings were divided almost equally between males and females. The victims' ages ranged from a single victim less than 1 week old to 13 victims 75 years or older. The greatest number of victims fell in the age range of 25 to 44 years, which constituted 91 (37.2 percent) of the victims. The age of the victim was unknown in 4 (1.2 percent) of the homicides. By race, white victims were divided almost equally between males and females in poisoning homicides. Victims of other races (American Indian or Alaskan Native and Asian or Pacific Islander) were as likely to be males as females.

Offender Attributes

The data also revealed that victim characteristics may dictate some contingency related to offender characteristics. That is, when victims were female, the offenders were predominantly male. By contrast, if victims were male, the offenders were divided almost equally between males and females. Regardless of the sex of the victim, the poisoning offender was predominantly white. When examining race, it appeared that homicidal poisonings, like other homicidal behavior, usually did not cross racial lines, with the offender predominantly of the same race as the victim. However, this information also indicated a slight increase from 1 percent to 3.5 percent among other races as victims compared with the 1980s analysis. Additional findings showed that whites were predominantly the victims of male offenders, blacks were almost equally the victims of male and female offenders, and people of other racial backgrounds were equally likely to be victims of female or unknown offenders.

By race, black poisoning offenders were males twice as often as females, and white poisoning offenders also were more likely to be males. By sex, the result that 168 (48.6 percent) of the poisoning offenders were male compared with 115 (33.2 percent) female offenders would seem to challenge the perception that primarily females use poisons. Of course, these cases represented only those murders that became known to law enforcement. It may be that females are the predominate poisoners, but are more successful at getting away with the crime. Furthermore, this information reflected a 50 percent increase in the participation of females in this criminal homicidal behavior compared with data from the 1980s. It must be noted, of course, that the sex of 63 (18.2 percent) of the offenders remained unknown. The offenders' ages ranged from one offender between the ages of 10 and 14 to four offenders 75 years or older. The age category of 20 to 34 years accounted for 111 (32.1 percent) of the offenders. The age of the offender was unknown in 73 (21.1 percent) of the homicides. These patterns remained relatively stable in comparison with those of the 1980s.

However, as a word of caution, because the authors found the percent of poisoning offenders with unknown characteristics to be 20 to 30 times higher than those with unknown characteristics among all homicide offenders, some of these demographic findings must remain tentative. This problem is most likely due to a lack of witnesses to provide insight into offender characteristics.

Relationship of Poisoning Victim to Offender

Homicides within families occurred with some frequency and accounted for 125 (36.1 percent) of the poisonings in the 1990s. The four most frequent relationships within the offender's family were son (9.5 percent), daughter (7.2 percent), wife (6.9 percent), and husband (5.2 percent). However, while many people may widely believe that poisoning is predominantly a household or domestic crime, this study found that of the reports where the relationship of the offender to the victim was known, more of the victims came from outside the family (63.9 percent) than from within the family (36.1 percent) of the offender. Victims outside the family of the offender accounted for 221 (63.9 percent) of the poisoning homicides. The five most frequent relationships outside the family were acquaintance (69, or 19.9 percent), unknown (66, or 19.1 percent), other (31, or 9 percent), friend (22, or 6.4 percent), and girlfriend (13, or 3.8 percent).


These results are in stark contrast to the findings from the 1980s that showed just 39 percent of victims outside the family of the offender. The earlier analysis disclosed a more equitable distribution of relationships, whereas this study revealed substantially more victimizations of individuals outside the family. But, once again, 66 homicide victims (19.1 percent) in the 1990s had an unknown relationship to the offender. So, the prevalence of unknown characteristics may dampen the significance of some of these patterns. In particular, the variance with the findings of the 1980s may be due to fluctuations in missing data relative to these cases, rather than true compositional changes in homicidal-poisoning behavior.

Type of Poison

Thirty (8.7 percent) of the female offenders and 38 (11 percent) of the male offenders employed a chemical (nondrug) poison. Eighty-five (25 percent) female offenders and 130 (37.6 percent) male offenders used a drug/narcotic as their homicidal agent. Although it was not possible from the SHR to determine the exact identification of the poison used, male offenders chose chemical (nondrug) poisons in a ratio of 5 to 4 compared with female offenders. While male offenders used a drug/narcotic in a ratio of almost 3 to 2 to female offenders, this still represented a 33 percent increase in the use of drug/narcotic poisonings by women when compared with data from the 1980s. Because the SHRs did not identify the exact poison used in the homicides, this important piece of information must come from a more in-depth analysis of the specific case reports on file in the various jurisdictions.

As to what can serve as a potential homicidal poison, an early, but accurate, definition can suffice: "What is there that is not a poison, all things are poison and nothing without poison. Solely the dose determines that a thing is not a poison." (6) Thus, any chemical substance has the potential of becoming the means of committing a poisoning homicide. Clearly, the prime candidate for the most effective weapon in homicidal poisonings is the chemical with the greatest lethality, the smallest dose, and the least likelihood of detection.

Geographic and Temporal Features

A total of 44 (88 percent) of the 50 states reported poisoning homicides for the decade of the 1990s. The seven states with the most reported cases, accounting for 178 (51.5 percent) of the total reported homicides, were California with 63 (18.2 percent), Washington with 34 (9.8 percent), Texas with 23 (6.6 percent), Pennsylvania with 22 (6.4 percent), and Arizona, Michigan, and New York with 12 (3.5 percent) each. Upon analyzing the 346 poisoning homicide reports by geographic region for the United States, the authors found that the Northeast had 52 (15 percent), the Midwest 56 (16 percent), the South 87 (25 percent), and the West 151 (44 percent). These findings were very similar to the analyses of the 1980s with the exception of an increase of 9 percent in reported cases from the western United States.

The fact that UCR received fewer SHR reports from one geographic area over another, however, does not necessarily mean lower poisoning homicide rates in any specific region. Factors that could impact the number of reports received from a jurisdiction include legislation requiring autopsies or toxicology screens on all deaths of unknown cause, the sophistication of analytical toxicology laboratories in the area, or the workload of the local law enforcement or forensic pathology personnel.

Modus Operandi

The number of homicide reports per year for the decade varied from a high of 41 in 1995 to a low of 26 in 1999. The average number of poisoning homicide reports per year was 34.6. Yet, the authors found little year-to-year variation in the data reported.

The incidence of poisoning homicide reports by month for the decade varied from a high of 40 in December to a low of 16 in August. The average rate of poisoning homicide reports by month was 28.8.

The data collection format of the SHRs made it impossible to determine an exact motive in 220 (64 percent) of the crimes because of the generalized categories, such as "other, not specified," "other," or "unable to determine circumstances." This important information relating to motive likely will have to come from a more indepth analysis of specific cases among local jurisdictions. Interestingly, only two (0.6 percent) SHRs reported the circumstance as related to a "lover's triangle," which appeared contrary to the general perception that poisons often are used in domestic situations to remove spouses or significant others.

Because of the large number of reports that fell into generalized unknown categories, the authors also could not determine the exact motive as it related to the relationship of victim to offender. Additionally, they could not ascertain how the poison was administered. However, a summary of findings concerning the demographics of homicidal poisonings depicts the consistency of patterns in these crimes and may provide an opportunity for investigators in developing leads that may reveal the methods used by these killers.


From this study, the authors concluded that the incidence of reported homicides due to poisoning comprised only a small portion of the SHR data for the decade. They wondered, though, if more of these types of homicides remained undetected because of the many holes in the investigative net through which the homicidal poisoner can slip. Also, many of the demographics of poisoning offenders were largely unknown, at least when compared with that of overall homicides during the decade. This may have indicated that homicide investigators had discovered a poisoned victim but could not identify the offender. An old and wise adage related to homicide detection states that "all deaths are homicides until facts prove otherwise." As evident from the cases identified at the outset of this research and the statistical analysis performed, perhaps this adage could prove more relevant to poisoning cases rephrased as "all deaths, with no visible signs of trauma, may be considered poisonings until facts prove otherwise."

The authors also felt that many other factors may be important to the identification of a poisoning homicide offender, such as the offender's socioeconomic status, IQ, level of education, professional training, personality (introversion/extroversion), ethnicity, prior criminal history, marital harmony, and psychological makeup. Unfortunately, SHRs do not contain this information; it can be generated only by in-depth research into actual circumstances surrounding homicidal-poisoning cases. Such analyses may assist law enforcement personnel in their investigations by arming them with a clearer picture of the poisoner. Finally, while this work has focused on individual incidents of homicidal-poisoning behavior, the importance of these patterns may be even more significant in the context of the 21st century. That is, the potential for toxic substances becoming a weapon of mass destruction may prove more of a substantial threat than in the past. In addition, the expanding elderly population may provide additional victims for those who wish to commit homicides that appear as deaths from natural causes. Understanding some of the attributes of homicidal poisoners may enhance the ability of the law enforcement and forensic communities when they are called upon to assist in the prevention and investigation of homicides.
Demographics of Homicidal Poisonings (1990-1999)

Attribute Victim Offender

Age 25-44 20-34 (8)
Sex Male/Female (9) Male (10)
Race White (11) White (12)
Circumstances Unknown (13) Unknown
Relationship 63 percent outside family (14) 36 percent within family
Weapon 75 percent drug/narcotic 25 percent nondrug (15)
Unknown 20-30 percent higher for both than that of all homicides

The authors thank the FBI UCR staff for providing SHR data relating to poisoning homicides. Additionally, they express appreciation to John Trestrail for his insights on earlier drafts and his contributions to earlier works in this area. Finally, they gratefully acknowledge those Behavioral Science Unit members who assisted at all stages of the process, including Intern Emily Noroski who reworked initial drafts and Special Agents Harry Kern and Sharon Smith who reviewed the final product.


(1) J. Glaister, "Methods and Motives," in The Power of Poison (New York, NY: William Morrow and Company, 1954), 153-182.

(2) Some earlier attempts to identify characteristics of poisoners include those by J. Rowland who found that poisoners likely had an unfortunate married life, failed to make an impression on life, possibly were connected with the medical world, were vain, possessed a mind without sympathy or imagination, and likely were spoiled by their parents, see "The Mind of the Poisoner," in Poisoners in the Dock (London, UK: Arco Publications, 1960), 230-237. Alternatively, C. Wilson described poisoners as prone to daydreaming and fantasy; possessing an artistic temperament; and being weak-willed, cowardly, and avaricious, see "Poisoners," in The Mammoth Book of Crime (New York, NY: Graf Publishers, Inc., 1988), 476-484. While these depictions may have been anecdotally accurate when offered, the question remains of whether current law enforcement perceptions and medicolegal statements about poisoners' characteristics still are valid and reliable. For recent exceptions, see A. Westveer, J. Trestrail, and A. Pinizzotto "Homicidal Poisonings in the United States: An Analysis of the Uniform Crime Reports from 1980-1989," American Journal of Forensic Medicine and Pathology 17, no. 4 (1996): 282-288; and J. Trestrail, Criminal Poisoning: Investigational Guide for Law Enforcement, Toxicologists. Forensic Scientists, and Attorneys (Totowa, NJ: Humana Press, Inc., 2000).

(3) UCR data, believed to be the most reliable source of information concerning incidents that come to the attention of the police, form the basis for all analyses presented in this article. For additional information on UCR, see U.S. Department of Justice, Federal Bureau of Investigation, Crime in the United States, 2002 (Washington, DC, 2003).

(4) See A. Westveer, J. Trestrail, and A. Pinizzotto "Homicidal Poisonings in the United States: An Analysis of the Uniform Crime Reports from 1980-1989," American Journal of Forensic Medicine and Pathology 17, no. 4 (1996): 282-288 for all references in this article to data on homicidal poisonings occurring from 1980 through 1989.

(5) For the purposes of this study, in those reports where there were an unknown number of offenders, the authors assumed that at least one offender was involved. Therefore, they included all of these cases, even though the exact number of offenders remained unknown.

(6) The physician Paracelsus (1493-1541) made this observation in 1538.

(7) It is estimated that only about 50 percent of the human population can detect the odor of cyanide. Therefore, the possibility exists that the use of this poisonous substance often may go undetected.

(8) Age or sex unknown in approximately 20 percent of the cases.

(9) If victim was male, offender was no more frequently male or female; if victim was female, offender was more frequently male.

(10) More frequent than female, but 50 percent increase in female offending compared with analyses of 1980s.

(11) If victim was white, offender was more frequently male; if victim was black, offender was no more frequently male or female. Black male victims occurred two times more than black female victims; white or other race males occurred equally with white or other race females. Other race victims increased from 1 percent to 3.5 percent compared with the analyses of 1980s.

(12) Both white and black offenders were more frequently male.

(13) Circumstances were not informative in 64 percent of cases due to being reported as unknown/other/missing. Yet, three times more husbands as wives were reported as victims in lover's triangle circumstance, along with some acquaintance victims in this circumstance.

(14) Relationship reported to be 39 percent outside family in the analyses of the 1980s.

(15) Drug/narcotic type poisoning involving female offenders increased 33 percent compared with the analyses of the 1980s.


Because they often display few visible signs, homicidal poisonings remain one of the most difficult crimes to detect and prosecute. All too often, authorities may certify a death as due to a natural or unknown cause, resulting in important evidence of the crime being buried with the victim. Therefore, a great number of homicides by poisoning are detected only upon specific toxicological analyses carried out after the exhumation of the victim's remains.

Selected from FBI and police files, as well as from public source court documents, these cases identify incidents in which the nature of the initial poisoning was either not detected or misdiagnosed. In most cases, the initial causes of death were thought to be accidental or due to natural causes, but were determined later (through considerable legal and investigative effort) to be homicides where poison was the weapon of choice.

Case #1

In a small country town, a white male suddenly became extremely ill with what his family claimed was pneumonia. Upon admission to the local hospital, he received treatment of antibiotics and pain killers. Ten days after the onset of his symptoms, he succumbed and was declared to have died from his illness. Unbeknownst to authorities, the victim's wife was involved in an adulterous affair and wished to marry her lover. After her husband's death, she returned some highly toxic herbicide to a fruit grower who became suspicious and contacted the police. Upon further investigation, the police learned that the victim's wife had collected on a $55,000 insurance policy and was pressuring her paramour into marriage. The police had the husband's body exhumed and discovered the highly toxic chemical paraquat in his body. As a result of these findings and other evidence, the police arrested and charged the wife with the death of her husband. She was later convicted and sentenced to 5 years' imprisonment and treatment in a mental hospital.

Case #2

Officers were called to a residence at 3:30 a.m. to treat an 8-month-old baby who reportedly had stopped breathing. The boy was transported to the local hospital and died later that morning. It was presumed that the infant had suffered from sudden infant death syndrome (SIDS). An autopsy later revealed that the child had a blood ethanol level of 0.12 (120 mg/dl). Further investigation led the police to suspect that the father had given the child a toxic dose of peppermint schnapps. The father was arrested and charged with negligent homicide for the alcohol poisoning of his son.

Case #3

Police found a 33-year-old woman dead on her waterbed. The investigating officer noticed a black substance around her mouth and nose and, recalling similar evidence from a case 12 years earlier, suspected possible cyanide poisoning. During the autopsy, personnel detected the distinctive bitter-almond odor common to cyanide poisonings. (7) Laboratory tests confirmed the presence of cyanide in the victim's blood, but not in her stomach contents. Due to this finding, investigators thought that the victim somehow was forced to inhale hydrogen cyanide gas. They later discovered that her husband worked at an exterminating company where hydrogen cyanide was readily available. Combining this information with evidence of both marital and financial problems, the police later arrested the husband. Prosecutors have sought a first-degree murder conviction and a possible life sentence.

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Author:Jensen, Carl J., III
Publication:The FBI Law Enforcement Bulletin
Geographic Code:1USA
Date:Aug 1, 2004
Previous Article:The Bulletin notes.
Next Article:Unidentified homicide victim.

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