People v. Myers (1980), 92 Ill. App.3d 229, 415 N.E.2d 1108; People v. Natoli (1979), 70 Ill. App.3d 131, 387 N.E.2d 1096; People v. Spahr (1978), 56 Ill. App.3d 434, 371 N.E.2d 1261; People v. Hall (1962), 25 Ill.2d 297, 185 N.E.2d 143. • 2 While the People are correct that there is no rule establishing entrapment as a matter of law solely because the government provided the controlled substance which the accused was charged with delivering ( People v. Cross (1979), 77 Ill.2d 396, 396 N.E.2d 812), it is persuasive evidence that if the substance was supplied by the government or its paid informer and the State fails to call the informer to rebut the defendant's testimony that the informant supplied the drugs to the defendant, a conviction for selling the drugs may not be sustained ( People v. Dillard (1979), 68 Ill. App.3d 897, 386 N.E.2d 920; People v. Spahr (1978), 56 Ill. App.3d 434, 371 N.E.2d 1261). We also subscribe to the rule of law that an appellate court must not substitute its judgment for that of the trier of fact on questions involving the weight of the evidence or the credibility of the witnesses and that a reversal of the defendant's conviction should not result unless the evidence is so improbable as to raise a reasonable doubt of guilt.