To be effective, the alibi evidence must demonstrate the impossibility of the accused's presence at the scene of the crime at the time it was committed. Arney v. State, 580 S.W.2d 836, 840 (Tex.Crim.App.1979); Villarreal v. State, 821 S.W.2d 682, 684 (Tex.App.-San Antonio 1991, no pet.). The defense of alibi is designed to show that the defendant, during the entire time that the crime was being committed was so far from the place where the crime occurred that he could not have participated in the crime. Villarreal, 821 S.W.2d at 684. If the alibi evidence, although taken as true, does not sufficiently cover the time at or before the crime to render the defendant's presence impossible or highly improbable, then it proves nothing. Id. The court of criminal appeals recently held that a defendant is no longer entitled to a jury instruction on alibi. Giesberg v. State, 984 S.W.2d 245, 250 (Tex.Crim.App. 1998). A separate instruction on alibi as a defense would draw unwarranted attention to evidence that appellant was at another place when the crime was committed, and would therefore constitute an improper comment on the weight of the evidence. Id.