Why did Ketanji Brown Jackson believe a key witness’s intellectual disability mattered in a criminal trial?

In a dissent regarding a murder conviction, Justice Ketanji Brown Jackson argued that the witness’s intellectual disability was critical because it may have impaired the individual's ability to accurately perceive facts, distinguish reality from fiction, and recall events.1

Jackson contended that the prosecution’s failure to disclose this information prevented the jury from properly evaluating the witness's testimony. She maintained that there was a "reasonable probability" that the trial's outcome would have been different had the jury been aware of the disability, and she criticized the lower court for applying an overly stringent standard when reviewing the impact of this suppressed evidence.1