The following excerpt is from United States v. Masino, 275 F.2d 129 (2nd Cir. 1960):
Indeed, where the principal witnesses appearing in behalf of the prosecution have a criminal record or have engaged in illegal practices and are accomplices to the crime charged, it is essential to a fair trial that the court allow the defendant to cross-examine such witnesses as widely as the rules of evidence permit. Montgomery v. United States, 5 Cir., 1953, 203 F.2d 887.
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