As I’ve mentioned before, when you are quoting material, it has to be an exact quotation. So what happens when the author of that exact quotation has made an error? That’s where our Latin friend sic comes in. The word sic means “thus” or “in such a manner.” It means that the writer knows that the quoted material is wrong, but it is the original author’s mistake, not the current writer’s mistake. Just be careful about using sic where the word or phrase you think is wrong may just be an archaic spelling or usage–but not necessarily grammatically incorrect.
According to Bryan A. Garner in A Dictionary of Modern Legal Usage ((2nd edition). Oxford University Press US, 2001), in state-court opinions before 1944, sic appeared 1,239 times in the Westlaw database; in those from 1945 to 1990, it appeared 69,168 times. I can only imagine that its usage has increased more dramatically still in the last 25 years.
Using sic should not be thrown around carelessly or to attempt to show an air of superiority. Such usage is called “benighted use” and is thought to have accounted for a large part of the increase in the use of sic.
As for formatting, modern American usage and The Gregg Reference Manual have the word sic in italics and surrounded by brackets–[sic]. Some authorities say that it is now such common usage that it is not formatted in italics. The Bluebook shows sic not italicized but enclosed in brackets–[sic]. Since The Bluebook is the standard for legal citation, it would appear that when you use it in legal documents, sic does not need to be italicized. The Bluebook also says that “[sic]” should follow “significant mistakes” in original language, so put “[sic]” right after the word with the issue and not at the end of the sentence or passage. The reader needs to know that you know it is an error at the point it is an error and not lines or words later.
Use [sic] where necessary and when necessary. It does have an important use and is a useful tool in our work, just do not overuse it to prove you’re smarter than anyone else. Nobody likes a showoff!