The admissibility requirement that expert evidence be shown to be reliable applies to the manner in which principles are applied as well as to the question of whether the principles that were sought to be applied are reliable; i.e., reliable principles must be applied in a reliable way and the application of reliable principles must be based on reliable or sufficient data.

United States v. Lechoco, 542 F.2d 84, 86-88 (D.C. Cir. 1976) (conviction for kidnapping after accused held the Philippine Ambassador to the United States as a hostage; accused alleged that the trial court erred in excluding evidence of his truthfulness and honesty during the insanity phase of the trial;...Subject to limitations, evidence that tends to repair a witness's credibility is admissible after the credibility of the witness has been attacked.

United States v. Aboumoussalem, 726 F.2d 906, 908, 912 (2d Cir. 1984) (upholding trial court's exclusion of irrelevant evidence that defendant was duped into transporting contraband by his co-conspirators because "it tends to make the existence of a consequential fact, defendant's knowledge, less...The prohibition against circumstantial character evidence -- the prohibition, codified in Federal Rule of Evidence 404, against the use of a person's character to show that person's conduct -- does not apply to non-parties.

United States v. Bruguier, 161 F.3d 1145, 1148-1150 (8th Cir. 1998) (upholding trial court's ruling which allowed the government to cross-examine the accused's opinion character evidence witnesses on their knowledge about specific incidents in order to explore the bases for holding such opinions ).When an exception to the character evidence prohibition makes evidence of a criminal defedant's character admissible, the testimony of a witness on direct examination about the defendant's character must take the form of reputation or opinion and it cannot consist of specific instances of the defendant's conduct.