Ninth Circuit, Appeals Court rules on ineffective assistance of counsel claims based on failure to introduce brain scan evidence in an Arizona case (Smith v. Ryan)

The Policy

What it does

Rules on the prejudicial value of the failure to introduce brain scans as mitigating evidence in a criminal appeal.


Smith v. Ryan (823 F.3d 1270) informs the debate on the value of various types of brain scan evidence in the courtroom. In Smith, the court considered whether the failure of Smith’s counsel to introduce a positron emission tomography (PET) scan and diffusion tensor imaging (DTI) studies potentially showing organic brain damage, known also as organic brain syndrome, in the penalty phase of the trial constituted ineffective assistance of counsel. Specifically:

  • The Ninth Circuit Court of Appeals held the PET and DTI scans of the defendant would have been largely cumulative of testimony by defendant’s neuropsychiatric expert. This testimony had already placed Smith in the “brain-damaged range,” indicating mild to moderate impairment. Since the brain scans were cumulative of testimony already heard, the court held that their introduction would not have had a reasonable probability of reversing the decision.


The Science

Science Synopsis

Over the last two decades, neuroscience has played an increasingly important role in the courts. In particular, brain scans are the most common type of neuroscience evidence introduced into the court room.

These neuroimaging techniques can produce ‘maps’ of the brain, capturing brain matter, blood vessels and the overall structure of the brain; or tracing brain activity using different biomarkers. This case featured two types of brain scans: PET and DTI scans. PET scans (positron emission tomography) use a radioactive biomarker that produces detailed images of tissues and organs by tracing metabolic activity in the body over time. PET scans can reliably image structural features of a brain, such as tumors or physical brain damage. DTI scans (diffusor tensor imaging) are a type of magnetic resonance imaging that image white matter, the connecting fibers between the neurons in the brain. Aging, many types of neurodegenerative disorders, like Alzheimer’s, and/or damage that results in organic brain syndrome, affect the white matter of the brain, and those changes can be detected by DTI scans.

Organic brain syndrome (OBS), which is synonymous with organic brain damage, describes a decrease in mental functioning for a reason other than a psychiatric illness. Detecting OBS—which includes diseases as diverse as alcoholism and epilepsy, as well as other conditions like concussions—can be done with a range of brain scans or neuropsychiatric testing looking for mental impairment. In the courtroom, brain scans and neuropsychiatric testing are used, sometimes alone and sometimes in combination, to determine the presence and degree of brain damage and related mental impairment. Brain scans like those listed above are used to detect brain injury, either by tracing the brain’s metabolic functioning or looking for physical signs of damage. Diagnosis of impaired mental state depends on the location and severity of brain damage detected by the scan; however, often more cognitive testing is needed to confirm a diagnosis. Neuropsychiatric testing, in contrast, identifies mental impairment through cognitive tests and then implicates the location and degree of brain damage based on the results.