The Admissibility of Expert Witness Testimony Based on Adolescent Brain Imaging Technology in the Prosecution of Juveniles: How Fairness and Neuroscience Overcome the Evidentiary Obstacles to Allow for Application of a Modified Common Law Infancy Defense

• Publication year: 2010

Sally Terry Green⁰

Adolescent brain imaging technology is an evolving area of science that reveals levels of maturity in the adolescent brain. Its potential effect on criminally culpable behavior is the source of extensive debate. The technology can inform judges and jurors on essential differences between how adults make decisions regarding their conduct as distinct from adolescents. United States Supreme Court precedence provides a relevant framework from which we can extrapolate fairness principles and their operation in developing a meaningful juvenile defense under which the technology can be considered. These principles should guide decisions made by the trial courts under the states' applicable rules of evidence regarding the admissibility of scientific data like adolescent brain imaging technology. Admitting the technology and expert witness testimony in the context of an Infancy Defense model provides the fact finder with the data necessary to make a more in depth determination of adolescent criminal capacity.

Most Infancy Defense statutes currently implemented by the states create a gap comprised of fourteen to eighteen-year-olds by failing to address this population of adolescents whose deficiencies in judgment and decision-making pose the most credible argument for criminal exoneration. Offering adolescent brain research as part of an Infancy Defense model provides juveniles with an opportunity to combat harsher penalties imposed by the states and facilitates imposition of legal standards that require consideration of the differences between children and adults. If juvenile offenders are to be truly considered less blameworthy than adults, preservation of the Infancy Defense is crucial. This is true even when they should be held accountable for their actions. By allowing the juvenile offenders to offer expert witness testimony based on adolescent brain imaging as part of the meaningful defense, the fact-finder can more fairly assess adolescents' decision-making capacity. Consequently, we must allow the admissibility of adolescent brain imaging in order to guard against overestimation of an adolescents' criminal culpability.

I. Introduction

The morning and evening news is littered with news of adolescent casualties. Although not always the loss of life that we usually expect to hear on the news, oftentimes the stories involve extreme acts of violence committed by adolescents with ensuing outrage from the adult community. Consider when one adolescent's conduct incites the emotion and misjudgment of another. Wayne Treacy did not expect that his life would potentially come to an end when he received a nasty text message from his girlfriend's cohort.¹ After all, he was already trying to cope with and grieve the recent suicide of his older brother.² The nasty text message erupted an unmanageable and, arguably, untenable response in Wayne causing him to beat Josie Lou Ratley so horribly that she currently fights to regain normal daily function.³ Undoubtedly, Josie's adolescent years of life before the beating are immeasurably altered—adolescent casualty number one.⁴

Wayne Treacy is being tried as an adult in a Florida criminal court on the charge of first degree attempted murder.⁵ The fifteen-year-old juvenile defendant faces the potential consequence of life without parole—adolescent casualty number two.⁶ While adolescents make poor decisions every day, rarely do their judgments amount to the events described in this recent Florida case. One psychologist compares the adolescent brain to that of a toddler—"unstable, dysfunctional and completely unpredictable."⁷ In the face of impulsivity and poor judgment, our criminal justice system can address cases like the one in Florida by, first and foremost, considering the decision-making function of the juvenile defendants like Wayne Treacy as that of an adolescent.

No one truly knows whether Wayne Treacy intended to mercilessly beat Josie Lou Ratley. A child may intend to commit an act but is frequently not capable of grasping the consequences of his actions or differentiating between right and wrong behavior.⁸ Admitting expert witness testimony of adolescent brain imaging technology under a modified Infancy Defense allows for preventing more adolescent "casualties."

A. The "Meaningful" Infancy Defense Model

Early in the fifth century, Roman law provided that children under seven could not form criminal intent or malice.⁹ English common law in the thirteenth century allowed a pardon for juvenile criminals which later evolved into a presumption against young offenders' criminal liability.¹⁰ in the seventeenth century, the common law provided a rebuttable presumption of criminality for fourteen-year-olds.¹¹ Those older than fourteen were liable as adults.¹² By the eighteenth century, the prosecution had to prove that the accused understood the wrongfulness of his act in order to rebut the presumption of incapacity.¹³ The common law infancy Defense erupted in the American colonies as a result.¹⁴

A few states codified the defense in their first penal codes.¹⁵ By the twentieth century, reformers were advocating for youngsters to be "treated" rather than punished.¹⁶ Even still, advocates in jurisdictions like California encourage progressive juvenile justice policies with an eye toward modern science that regards teenagers as less culpable than adults.¹⁷ The common law defense or a modified version is available in forty-five states.¹⁸ on the other hand, five states have modified the infancy Defense by lowering the age of presumed incapacity from fourteen to twelve.¹⁹ Unfortunately, the desired rehabilitative models for juvenile dispositions have deteriorated in the face of harsher penalties imposed by the states.²⁰ A modified infancy Defense model allows juvenile and adult courts to consider standards for imposing criminal culpability with comprehensive understanding of the cognitive context under which adolescents make decisions. For as long as we choose to prosecute juvenile offenders for their actions as if they are adults, we must allow adolescent brain imaging to be part of a meaningful defense so that we can fully comprehend the adolescent mind upon which criminal sanction is imposed.

B. The Infancy Defense, Adolescent Brain Technology and U.S. Supreme Court Precedence

Adolescent brain imaging technology is an evolving area of science that reveals levels of maturity in the adolescent brain and its effect on criminally culpable behavior.²¹ Under the law, we have historically treated children in our American criminal justice system differently than adults because they were viewed as cognitively and emotionally immature.²² The United States Supreme Court recently heard arguments made in two consolidated Florida cases challenging the sentencing of juveniles to life without parole.²³ In the past, juvenile offenders in some jurisdictions have been subject to imposition of life without parole.²⁴ The arguments put forth in the Florida cases refuted life without parole in non-homicide cases and highlighted arguments of diminished culpability and maturity which were successfully asserted in Roper v. Simmons²⁵ Recently, on May 17, 2010, the Supreme Court determined that juvenile life without parole sentencing violated the Eighth Amendment to the U.S. Constitution.²⁶ The Court followed its reasoning in Roper closely and referenced the limited culpability of juveniles and how developments in brain science illustrate juveniles' continuous maturation process past adolescence.²⁷

Offering adolescent brain research as part of an Infancy Defense²⁸ model provides juveniles with an opportunity to combat harsher penalties imposed by the states and facilitates imposition of legal standards that require consideration of the differences between children and adults in making moral judgments.²⁹ Our criminal law system considers whether the accused acted out of free will and whether the punishment is legitimate.³⁰ We punish individuals for wrongful acts if they understand the nature of their conduct, and in many states, if they are capable of controlling their impulses.³¹ When punishing adolescents, we must consider developmental research studies that identify three stages of child development and capacity: (1) children under seven who lack capacities to be culpable, (2) mid-childhood children who are unlikely to have that capacity, and (3) adolescents who are usually regarded as having less capacity than adults.³² This article asserts that the Infancy Defense provides a legal framework for considering the relevant scientific data and the graduated model of capacity under which children make decisions. The defense allows for an adjudicatory and prosecutorial process that reflects our knowledge of childhood development.

Information provided by brain imaging technology on the juvenile offenders' brain function can be offered through use of expert witness testimony, which should be admitted to establish the juvenile's inability to cognitively appreciate and process the wrongfulness of juveniles' conduct. Expert testimony is necessary to bolster juvenile defendants' arguments that the normal genetic structure of their adolescent brains supports exculpation over contrary arguments asserted by the prosecution. Such testimony would corroborate already existing evidence in support of the juvenile's defense by showing deficient judgment, decision making, and irresponsibility—all relevant evidence to a modified Infancy Defense asserted by a juvenile defendant.

During the past decade, several commentators have examined the progression of scientific brain imaging technology and its use in the courtroom.³³ Quite expectedly, critics have identified specific problems with using this technology under our current legal standards.³⁴ While the technology evolves, it appears that the current state of brain imaging has limited utility in the courtroom in light of deep concerns regarding the complexities...