Whether the defendants in the Duke lacrosse case are guilty or innocent, Durham District Attorney Mike Nifong should disqualify himself, or be disqualified, from the case.

On Friday, Nifong's own witness essentially accused him of breaking the law. An actual conflict of interest now exists between Nifong's need to defend himself against possible charges of misconduct and his obligation to prosecute the case fairly and effectively.

In court Friday, the head of a lab that Nifong retained to analyze DNA samples testified that he and Nifong intentionally decided to exclude from the expert's report the fact that DNA analyzed from the clothes and body of the accuser did not belong to any of the defendants but came instead from unidentified males.

N.C. General Statute 15A-903 requires that a prosecution expert provide a report of the results of any tests performed and that the prosecutor furnish that report to the defense. Deciding to exclude these results is deciding to violate this law.

A prosecutor also has an obligation under the U.S. Constitution and under N.C. Rule of Professional Conduct 3.8 to disclose to the defense evidence which tends to suggest the innocence of a defendant — including evidence that calls the credibility of a state witness into question. DNA results showing the absence of DNA material from the accused and the presence of DNA material from other men goes to the credibility of the accuser's account and therefore needs to be disclosed.

In addition to these disclosure requirements, a prosecutor has an ethical obligation not to ignore evidence which suggests the innocence of the accused. A comment to Rule 3.8 provides that "a prosecutor should not intentionally avoid pursuit of evidence merely because he or she believes it will damage the prosecutor's case or aid the accused." It is not clear that Nifong has ever followed up on the DNA evidence described.