In origin, case really is two different words, one derived from a form meaning "receptacle" or "container," the other meaning "instance" or "example." In both senses, the word has been abused and overused. Case is slang in such expressions as "case the joint" ("to examine the place or premises") and "Jack's a case" ("Jack is an eccentric or peculiar person"). The phrase "the case of is nearly always verbiage and adds nothing to any statement: omit it in both speaking and writing.
Dictionary of problem words and expressions. Harry Shaw. 1975.