Is a knowingly false statement of fact a constitutionally protected claim?

The high court has made clear, however, that even as to public officials, knowingly false statements of fact are constitutionally unprotected. "The use of calculated falsehood, however, would put a different cast on the constitutional question. Although honest utterance, even if inaccurate, may further the fruitful exercise of the right of free speech, it does not follow that the lie, knowingly and deliberately published about a public official, should enjoy a like immunity.... For the use of the known lie as a tool is at once at odds with the premises of democratic government and with the orderly manner in which economic, social, or political change is to be effected.... Hence the knowingly false statement and the false statement made with reckless disregard of the truth, do not enjoy constitutional protection." (Garrison v. Louisiana, supra, 379 U.S. at p. 75, 85 S.Ct. 209.)