first degree. On occasion, a person with a disorder
may kill on the spur of the moment, motivated by a
command hallucination or a delusional belief. Such
people are capable of premeditating, but the mental
abnormality evidence simply tends to show that they
did not premeditate in fact on this occasion. And even
if premeditation is negated, the intent to kill is not.LLiimmiitteedd AAddmmiissssiioonn ooff
MMeennttaall AAbbnnoorrmmaalliittyy EEvviiddeennccee
If the rationale for the mens rea variant is
accepted, as a logical matter, the evidence should be
admitted to negate any mens rea that might have
been negated in fact. Indeed, this is the Model Penal
Code position. Nonetheless, virtually all jurisdic-
tions that have permitted using mental abnormality
evidence to negate mens rea have placed substantial
limitations on doing so, largely because they incor-
rectly fear large numbers of outright acquittals that
could result from following the pure logical rele-
vance standard for admission. Limited admission is
thus based on a policy compromise between consid-
erations of fairness and public safety: A defendant is
able to negate some but not all mens rea, which typ-
ically results in conviction for a lesser offense. The
effect of mental abnormality on culpability is thus
considered, albeit partially,anda potentially danger-
ous defendant does not go free entirely, albeit the
sentence is abbreviated.Partial Responsibility Variant
Some criminal defendants who acted with the mens
rea required by the definition of the crime charged
and who cannot succeed with the insanity defense
nonetheless have mental abnormalities that substan-
tially compromise their capacity for rationality. The
logic of the partial responsibility variant flows from
this observation. In general, the capacity for rational-
ity, the capacity to grasp and be guided by reason, is
the touchstone of moral and legal responsibility.
Mental abnormality potentially compromises moral
and legal responsibility because in some cases it ren-
ders the defendant so irrational that the defendant is
not a responsible agent. The capacity for rationality
is a continuum, however, and in principle, responsibil-
ity should also be a continuum, allowing for a partial
defense. Nonetheless, no generic partial excuse for
diminished rationality arising from mental abnormalityexists in any jurisdiction in the United States or in
English law. Thus, for example, a mentally abnormal
defendant who killed intentionally and with premed-
itation has no doctrinal tool to avoid conviction and
punishment for the most culpable degree of crime—
first degree murder—even if the killing was highly
irrationally motivated as a result of substantial men-
tal abnormality.
Courts are unwilling to create a generic excuse for
many reasons, including the belief that they do not have
the power to create new excuses, the fear that they will
be inundated with potentially confusing or unjustified
cases, and the fear that dangerous defendants might go
free too quickly and endanger the public. Furthermore,
courts believe that creating a genuine partial excuse is a
“legislative act” that exceeds judicial prerogative. In a
few jurisdictions, courts tried to develop a partial
excuse in the guise of adopting the mens rea variant, but
these attempts used extremely problematic mens rea
concepts, were confusing, and have largely been aban-
doned. Legislatures appear unwilling to enact a generic
partial excuse because, in general, legislatures are not
responsive to claims that are to the advantage of wrong-
doers and because legislators, too, fear the conse-
quences for public safety.PPaarrttiiaall RReessppoonnssiibbiilliittyy
DDooccttrriinneess aanndd PPrraaccttiicceess
Despite their reluctance to adopt a generic partial
responsibility doctrine, courts and legislatures have
adopted various doctrines or practices that are in fact
forms of partial excuse. Most prominent are (a) the
Model Penal Code’s “extreme emotional disturbance”
doctrine (Sec. 210.3.1(b)) and English “diminished
responsibility,” both of which reduce a conviction of
murder to the lesser crime of manslaughter; (b) one
interpretation of the common-law provocation/
passion doctrine, which reduces an intentional killing
from murder to voluntary manslaughter; and (c) the
use of mental abnormality evidence as a mitigating
factor at sentencing hearings.
The extreme emotional disturbance doctrine, pro-
mulgated by the Model Penal Code and adopted in a
small minority of American states, reduces murder to
manslaughter if the killing occurred when the defen-
dant was in a state of extreme mental or emotional
disturbance for which there was reasonable explana-
tion or excuse. Mental abnormality evidence is admis-
sible in most jurisdictions to establish that suchDiminished Capacity——— 219D-Cutler (Encyc)-45463.qxd 11/18/2007 12:42 PM Page 219