ies a case also testifies as a witness, and trial attorneys have been permitted to testi- fy only in certain circumstances.niii FN14. United States I. Porter, 139 U.S.App.D.C. 19, 4 9 F.2d 203 (1970 ; United States & Fiorillo, 376 .2d 180 (CA2 19 ; Gajew- sld ii . United States, 321 F.2d 261 (CA 196