legal context in which this subject arises is insanity.
Insanity in the law is a construct that relates to respon-
sibility or what might be termed moral culpability.
The law presumes that behavior is freely willed and
the product of a rational mind. A person might be
excused under the law if these presuppositions are
demonstrated not to be so in a particular case. Most
jurisdictions employ an insanity defense based on the
19th-century case of Daniel M’Naghten, who attempted
to assassinate Sir Robert Peel, the British Prime
Minister, but shot and killed Peel’s assistant, Edward
Drummond, by mistake. Under the test, a defendant
should be acquitted if he “was under such a defect of
reason, from disease of the mind, as not to know the
nature and quality of the act he was doing, or, if he
did know it, that he did not know he was doing what
was wrong.”
As a practical matter, the subject of past mental states
is complicated by the very different vocabularies that
lawyers and scientists bring to the subject. Lawyers
speak in terms of insanity and diminished capacity,
whereas psychologists employ an expansive vocabulary
designed to account for the wide variation in behaviors
observed. The law, therefore, presumes, and has con-
structed, a world in which mental capacity to reason
exists largely in two-dimensional space: A person was
sane or insane when he or she committed a particular
act. Psychology, in contrast, presumes, and has con-
structed, a world in which mental capacity to reason
varies widely in multidimensional space: A person
might suffer from a disability with multiple etiologies
and with varying effects on his or her capacity to reason.
Although insanity occupies much of the scholarly
attention regarding past mental states, much of the
syndrome literature similarly involves the effort to
explain preexisting thought processes. For example,
the BWS is used in many jurisdictions to demonstrate
that battering victims did not behave unreasonably
when they used deadly force against their batterers.
Part of the factual inquiry for triers of fact in these
cases, as defined by substantive law, is whether the
battered woman believed that she was in imminent
danger of harm at the time that she killed the batterer.
Since many of these cases involve circumstances in
which the defendant acted at a time when she did not
confront an immediate objective harm—if, say, the
killing occurred when the victim was sleeping—the
psychological proof is offered to support her claim
that she was reasonable in believing that harm was
nonetheless imminent. According to BWS advocates,this inference follows from available research in two
possible ways. First, as a general matter, the data sug-
gest that prolonged abuse renders battered women
constantly fearful, a psychological outcome that is a
natural consequence of the violence. Second, advo-
cates argue that specific clinical observations can sup-
port the individual defendant’s claim that she was in
constant fear and, thus, honestly and reasonably
believed that harm was imminent when she killed.
A fundamental challenge for psychologists regard-
ing past mental state concerns the inherent difficulty in
assessing a phenomenon that cannot be observed even
indirectly. In effect, when the law asks psychologists to
assess past mental states, it puts them in the role of
forensic investigator. Little research is available to sug-
gest that psychologists can fulfill this role in a reliable
fashion. Nonetheless, some scholars, most notably
Christopher Slobogin, argue that the inherent difficulty
of the task should lead courts to relax the usual rules of
admissibility. According to this view, psychologists
can still “assist the trier of fact” regarding past mental
states, even if the phenomenon defies direct observa-
tion or straightforward test.Past Behavior
Possibly the most controversial use of psychological
expertise is behavioral profile evidence or psychologi-
cal expertise that is offered as proof that a person com-
mitted some act, typically one that he or she is charged
with a crime for having committed. Most evidence
codes proscribe the use of past bad acts—referred to as
“character evidence”—and thus ostensibly prohibit
behavioral profiling for the purpose of proving that the
defendant probably committed the alleged crime
because he or she has a propensity to commit such
crimes. Nonetheless, courts still often admit such evi-
dence in one form or another. The most egregious
examples of this practice involve courts’ admission of
evidence such as rapist profiles to prove the substantive
offense.
More common, however, is court allowance of evi-
dence that serves dual purposes: one permissible and
the other not. For example, there is a growing use of
BWS by states to prosecute alleged abusers. BWS
would not ordinarily be allowed simply to support the
inference that because the defendant abused the wit-
ness in the past, he is probably guilty of the assault for
which he is on trial. This is prohibited character evi-
dence. However, in many cases, women who were268 ———Expert Psychological TestimonyE-Cutler (Encyc)-45463.qxd 11/18/2007 12:42 PM Page 268