Indeed, the Department of Justice urges that its prosecutors seek independent corroboration, either to witnesses or corroborating evidence, of a quality to assure that a guilty verdict is really well founded.

CNN: Transcript: White House Counsel Ruff's opening statement

He found none of the key witnesses credible and had virtually no independent corroboration on which to rely.

FORBES: Legal Tip: No Such Thing as a One-Person "Partnership"