Once past the due process issues presented by the confidential informant‘s mental health and prescription drug issues, the Court in U.S. v. Robinson went on to address the confrontation issues under the 6th Amendment raised by the trial court‘s refusal to allow the defense attorney to cross examine the confidential informant at trial on those issues.
The 10th Circuit Court of Appeals found that the district court had indeed violated the Confrontation Clause under the 6th Amendment when it forbade the defense from cross-examining the CI on his mental health history and use of prescription medications. Further, the court found that the prosecutor had failed to meet the high burden of proving beyond a reasonable doubt that these constitutional errors were not harmless errors.
The Court stated that the 6th Amendment guarantees the right of a defendant to “be confronted with the witnesses against him.” The primary right under the Confrontation Clause is the right to confront and cross examine the State‘s witnesses. And though the trial court may exercise its discretion through “reasonable limits” on the scope of questioning, cross examination is the primary means by which the credibility of witnesses is determined by the jury.
The Court found that the trial court had not violated the Confrontation Clause on the issue of illegal drug use since it allowed the defense to cross examine the confidential informant on these issue. However, the prohibition against cross examination of the confidential informant on his mental health issues and related prescription drug use violated the defendant‘s right to confrontation since the cross examination on the illegal drug use may have been much different with full access and knowledge to the informant‘s mental health records.
The Court stated, “Where the witness the accused seeks to cross-examine is the ‘star‘ government witness, providing an essential link in the prosecution‘s case, the importance of full cross-examination to disclose possible bias is necessarily increased.” The Court stated further that “a constitutional violation occurs when the defendant is prohibited from engaging in otherwise appropriate cross-examination that, as a result, precludes him from eliciting information from which jurors could draw vital inferences in his favor.”
In short, the informant‘s credibility was essential to the government‘s case. The defendant had a right to put the informant‘s credibility before the jury and the jury‘s view of his credibility was critical to the outcome of the case for both sides. Preclusion of the defense‘s review and cross examination on issues of mental health and drug use was a fundamental violation of both due process and the right to confrontation of witnesses.