Does the absence of an alibi instruction in a criminal case invalidate a defendant's alibi?

There have been occasions when the courts have viewed the absence of an alibi instruction as harmless. When such an instruction has not been requested or when the evidence of the defendant's guilt has been overwhelming or when the evidence in support of the alibi defense has been negligible or when the defendant's presence at the scene of the crime has not been an element of the offense which the government was required to prove, the courts have held that failure to provide an alibi instruction does not require reversal. United States v. Coughlin, 514 F.2d 904 (2d Cir., 1975); United States v. Cole, 453 F.2d 902 (8th Cir. 1972); United States v. Erlenbaugh, 452 F.2d 967 (7th Cir. 1971), aff'd on other grounds, 409 U.S. 239, 93 S.Ct. 477, 34 L.Ed.2d 446 (1972); United States v. Lee, 483 F.2d 968 (5th Cir. 1973).