In Stewart v. Commonwealth, 10 Va. App. 563, 394 S.E.2d 509 (1990), the Court addressed whether a defendant could question witnesses in a murder trial about an unknown substance found at a murder scene. The defendant sought to prove the victim was a drug dealer in order to prove that other individuals may have had motives for killing him. Id. at 567, 394 S.E.2d at 512. Although the Court held that such questioning was inappropriate, nevertheless, we ruled that "defense counsel made a sufficient proffer of the testimony excluded by the trial court by stating his unchallenged unilateral avowal that he expected the testimony to show that controlled substances were discovered at the crime scene which might implicate some other person as the possible criminal agent." Id. at 568, 394 S.E.2d at 512.