exculpatory

Definition from Nolo’s Plain-English Law Dictionary

A description of evidence in a criminal trial that serves to justify, excuse, or introduce a reasonable doubt about the defendant's alleged actions or intentions. Exculpatory evidence may ultimately show that the defendant is not guilty. No wonder police and prosecutors must, to uphold the defendant's constitutional right to due process, tell the defense about any exculpatory evidence they've discovered.

Definition provided by Nolo’s Plain-English Law Dictionary.