Some fact scenarios speak for themselves. From Williams v. Select Media Servs., LLC, 2008 U.S. Dist. LEXIS 14773 (M.D. Ala. Feb. 27, 2008):

Defendants move to sanction Plaintiffs' attorney ... for continuing to bring the RICO claim in this case, even though it has been dismissed by six previous federal district courts. *** In this case, a reasonable inquiry of the legal and factual grounds for the Complaint prior to its filing would have made [plaintiff’s counsel] aware that the civil RICO claim is frivolous. The same claim was dismissed by six federal district courts, and four of these six dismissals were appealed and affirmed by courts of appeals. These cases were dismissed under Rule 12(b)(6) for failure to state a claim upon which relief can be granted because the allegations lacked sufficient factual and legal bases. The decisions of these courts should have made [plaintiff’s counsel] aware that the claim in this case is frivolous. Therefore, the Court finds that [plaintiff’s counsel’s] conduct warrants sanctions under Rule 11.

Defendants directed to submit “itemized and verified report of expenses incurred in defending this action.”