When will a federal judge refuse to give jury instructions concerning eye-witness identification?

Field requested that the district judge give a lengthy and involved jury instruction concerning eye witness identification, commonly referred to as a Telfaire instruction. See United States v. Telfaire, 469 F.2d 552, 558-59 (D.C. Cir. 1972). The trial judge refused to do so, choosing instead to give a shorter form of eye-witness-identification instruction. Field contends that rejection of the Telfaire instruction in this case was error because the importance of the eye witness identifications and the lack of evidence corroborating those identifications made the shorter instructions inadequate. There is no need to depart from our established rule that the giving of jury instructions is discretionary, and that trial courts need not give the Telfaire instruction when the matter is covered by simpler instructions. United States v. Cassasa, 588 F.2d 282, 285 (9th Cir. 1978), cert. denied, 441 U.S. 909, 99 S.Ct. 2003, 60 L.Ed.2d 379 (1979); United States v. Collins, 559 F.2d 561, 565-66 (9th Cir.), cert. denied, 434 U.S. 907, 98 S.Ct. 309, 54 L.Ed.2d 195 (1977); United States v. Masterson, 529 F.2d 30, 32 (9th Cir.), cert. denied, 426 U.S. 908, 96 S.Ct. 2231, 48 L.Ed.2d 833 (1976).