A double-edged sword: the role of neuroimaging in federal capital sentencing.

I. INTRODUCTION H.LA. Hart has stated that certain mental conditions have an "excusing" effect on punishment, whereby "[t]he individual is not liable to punishment if at the time of his doing what would otherwise be a punishable act he is ... the victim of certain types of mental disease."1 The Supreme Court,2 however, upheld a state statute allowing for increased "punishment,"3 in the form of civil commitment, for sexually violent predators who suffer from a "mental abnormality."4 Thus, American jurisprudence is faced with a paradoxical role of mental conditions: serving to both aggravate and mitigate sentences. This dual purpose of mental conditions becomes a pressing legal issue as mental conditions associated with brain structure or function become more detectable with the emergence of neuroimaging.5 In federal capital sentencing, judges are obligated to consider aggravating and mitigating factors before imposing a death sentence.6 There are aggravating and mitigating factors that could be implicated by mental conditions, including future dangerousness, 7 and impaired capacity, 8 respectively. As a result, the academic question arises: What if a brain dysfunction, detectable by neuroimaging, indicates both future dangerousness and impaired capacity? Unfortunately for the law, such an area of the brain already has been identified: the frontal lobes. This Note has two limitations: its scope of brain-imaging and its scope of the judicial system. First, the focus is on damage to the frontal lobe, where much research has been conducted linking this area of the brain both to violent and aggressive behavior,9 and to the inability to completely control one's actions.10 second, this note will limit the cases examined to federal capital cases for homicide, as federal courts are statutorily required to consider mitigating and aggravating circumstances.11 Additionally, federal cases have articulated future dangerousness as an aggravating factor, and federal statutes list impaired capacity as a mitigating factor. In Part II, this Note will provide background information on both frontal lobes and the effects damage to the frontal lobes can have on one's behavior. Part III will examine current federal procedure for capital cases, the roles of aggravating and mitigating evidence, and how frontal-lobe dysfunction can fit into each category. Part IV explains the danger that neuroimaging evidence can pose: in the same case, serving to both aggravate and mitigate defendant's sentence. Part V discusses the obligations of defense counsel in neuroimaging cases, such as when defendant can raise an ineffective assistance of counsel claim for counsel's failure to introduce neuroimaging evidence and when defendant is legally entitled to psychiatric expert assistance. Part VI focuses on the mental health expert and the care, caution, and limitations that must surround expert testimony on neuroimaging evidence. Part VII considers outside areas to shed light on this discussion, such as civil commitments, juveniles, and philosophical bases for punishment. Part VIII concludes this Note with a recommendation on how potentially dualistic neuroimaging evidence should be treated in the American legal system. II. NEUROIMAGING OF FRONTAL LOBES Neuroimaging detects frontal-lobe dysfunction either through computergenerated visual representations of the brain's structure or of its function.12 Structural neuroimaging is conducted by either computerized tomography scanning ("CT") or magnetic resonance imaging ("MRI"), and generates images of the brain's soft-tissue structure.13 Functional neuroimaging is conducted by positron emission tomography scanning ("PET"), and captures the brain while in action, measuring cognitive activity.14 Brain activity is actually inferred from the presence of high metabolic rates in structures involved in the cognitive process.15 A hybrid of structural and functional neuroimages is functional MRI ("fMRI"), which combines structural representations with information about brain activity extracted from functional scans. …