and allows for stronger anchoring of the psychological
sciences with the biological sciences. Evolutionary psy-
chologists argue for distinctions between various types
of homicide. Inroads into the psychology of homicide
have been made by an attempt to understand the relation-
ships between the victim and the offender. There is a
debate among evolutionary psychologists on whether
there exist evolved psychological adaptations for homi-
cide or whether homicide occurs as a by-product of
adaptations selected for in response to other sets of social
adaptive problems (e.g., sexual jealousy, same-sex com-
petition, aggression). An evolutionary psychological
approach informs us of many areas in the psychology of
homicide that have not been fully explored. If homicides
were a recurrent feature of our ancestral environment, for
example, selection would have favored antihomicide
psychological adaptations (e.g., avoid being killed,
minimize the threats posed by others). Research on the
existence of these possible evolved psychological adap-
tations is currently under way.
In many homicides, the offender and the victim are
individuals with a history of previously close romantic or
familial relationships. There are many known factors
linked with homicide among romantic partners, includ-
ing sexual jealousy and prolonged abuse of women by
their partners. These variables demand a deeper under-
standing of interpersonal relationships that can add to the
body of research informing the psychology of homicide.
A particularly dangerous time for many women comes
when they terminate a romantic relationship. From an
evolutionary perspective, this termination prompts psy-
chological adaptations in men that may have functioned
in ancestral environments to retain a mate. These adapta-
tions may prompt behavior such as vigilance over the
partner’s whereabouts, reassessment of the relationship,
or, more dangerously, stalking behavior and homicidal
rage over the termination of the relationship and a newly
established relationship with a rival male.
Among homicides occurring between parents and
children, men are more likely than women to kill their
children when the children are older, whereas women are
more likely to kill their children when the children are
younger. Many of the results of analyses of filicides fol-
low from predictions made by evolutionary psycholo-
gists. Men, relative to women, may harbor psychological
adaptations that monitor genetic relationships between
themselves and their putative children (e.g., cues such as
female infidelity and their own similarity to the child).
The features of homicides by mothers perpetrated
against children are very different from those of homi-
cides perpetrated by fathers against children. Mothersmore often than fathers kill their children because of fac-
tors related to current states (e.g., absence of investing
father, resource demands from children) or future
prospects (e.g., bias toward future children rather than
current children). Prior to the work done by evolutionary
psychologists, no research platform had identified the
presence of stepparents as a risk factor for child homi-
cide. Researchers have documented a risk factor of fili-
cide that is 100 times greater when a stepparent resides
in the household.
Siblicides account for only 1% of all homicides, but
analysis of this type of homicide has given us glimpses
into the psychology of sibships. Among siblicides, for
example, older siblings are more often the perpetrators
earlier in life. In contrast, younger siblings are more
often the perpetrators later in life—perhaps as an attempt
to secure larger portions of inheritance that might other-
wise be channeled to older siblings. Additionally, fea-
tures of the precipitating conflict within the relationship
may be revealed by the method of murder. Among sib-
lings, for example, full siblings use a less brutal method
of homicide than stepsiblings or half-siblings.Future Directions and Integration
In addition to the theoretical strides that need to be
made in the area, there are many empirical obstacles
to be overcome. Data found in national and city-level
homicide databases often do not contain enough infor-
mation relevant for more detailed analyses of homi-
cides. These obstacles are correctable with greater
collaboration between law enforcement and social sci-
entists. Another problem with our collective under-
standing of homicide is media misrepresentations.
Those murder cases that are relatively rare (e.g.,
homicide of women and children, serial murders) are
often the cases covered the most by different media
sources. Very little is known by the public of the
actual risk factors and probabilities of homicide.
The prospect of future research on the psychology
of homicide is bright, with the overarching goal of
understanding the biological, psychological, and
social triggers producing homicidal cognitions and
behavior. More detailed pictures of the minds of
murderers will be made through the collaborative
efforts of criminologists, sociologists, anthropolo-
gists, forensic psychiatrists and psychologists, neu-
ropsychologists, clinical/counseling psychologists, and
evolutionary psychologists. With such collaborative
efforts focusing on the interplay between the biologi-
cal, psychological, and social correlates of homicide,358 ———Homicide, Psychology ofH-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 358