A jury found defendant guilty on two counts of possessing narcotics and the court sentenced him to consecutive eight-year terms.
On appeal defendant concedes the sufficiency of the state’s evidence of possession but contends the trial court prejudicially erred by admitting irrelevant evidence of police affidavits and a search warrant when he had challenged neither the propriety of his arrest nor the seizure of narcotics.
The substantive evidence was definite. When police officers forcibly entered a house, defendant and others scattered. The police found defendant and another flushing capsules down a toilet. They arrested defendant and found other capsules of “controlled substances” in his pockets. Case made.
For reasons not apparent to us, the state was not satisfied with the quantum of the cited evidence. In its opening statement, in its testimony in chief and in closing argument, statements by counsel and testimony of witnesses, references were made to the challenged affidavits and search warrant.
The arresting officers testified that before arresting defendant they had prepared affidavits concerning narcotics at the address in question, appeared before a circuit judge, swore to the affidavits, and the judge issued the search warrant which was introduced in evidence. At every step, defendant objected to reference to the affidavits and search warrant on the ground of irrelevance.
Two related questions arise. Were the challenged references relevant to the crime charged? If not, was there prejudicial or only harmless error?
As to relevancy: In Crowley v. Crowley, 360 S.W.2d 293[2] (Mo.App.1962) we held: “Relevancy is the relationship between the offered fact and the fact in issue to such a degree that the existence of the offered fact logically renders probable the existence of the fact in issue.” Here, the simple fact issue was whether defendant possessed narcotics. The “offered facts” were the police officers’ out-of-court statements that they believed someone at the named address did possess narcotics and that a judge had believed them. Had defendant challenged the police officers’ right to arrest him, or to seize contraband in his possession, the offered facts probably would have been relevant. But he did not.
The state now seeks to justify the offered facts by arguing that the officers’ possession of a warrant tended “to substantiate the officers’ testimony in regard to the circumstances of appellant’s arrest.” The officers arrested defendant the moment they •found him in possession of what they believed were narcotics. The search warrant, being based only on the officers’ previously stated beliefs, was utterly irrelevant to defendant’s arrest and to the charge of possessing narcotics.
We hold the offered facts concerning the police officers’ belief and the circumstances surrounding the issuance of the search warrant did not logically tend to establish the issuable fact that defendant thereafter unlawfully possessed narcotics. The challenged evidence was inadmissible, and we move to the related issue of whether the error in admitting it was prejudicial or harmless.
We consider the judicial role in determining on appeal whether the improp*349er admission of evidence was harmless error. For a court to so determine, of necessity it must be able to declare beyond doubt that the tainted evidence did not affect the jury in its fact-finding process. It is, of course, the jury’s sole prerogative to believe, or disbelieve, all or part of any item of evidence. An appellate court has no way of knowing — and should not speculate about — what evidence a jury did or did not believe and the extent to which that evidence entered into the jury’s decision-making process.1 The rationale of these principles is capsulized in the judicial pronouncements that “error in the admission of evidence should not be declared harmless unless it is so without question,” (State v. Degraffenreid, 477 S.W.2d 57[14] (Mo.1972)), and that the record must “demonstrate that the jury disregarded or could not have been influenced by the evidence.” (State v. Wynne, 353 Mo. 276, 182 S.W.2d 294[9] (1944)). How can we declare here that the tainted evidence was harmless without question or that the jury could not have been influenced by it?2
The state’s evidence that defendant possessed narcotics depended on the jury’s accepting as true the testimony of the two police officers. Their credibility or lack of credibility was the key to conviction or acquittal. To buttress that credibility the prosecution showed the officers had previously made affidavits concerning narcotics at the place in issue and that a judge had believed them by issuing a search warrant. Over defendant’s repeated objections, testimony of this “boot-strap” tactic was admitted into evidence. It was stressed in opening statement, in testimony and in closing argument.
We hold the state has not shown without question that the error was harmless, that is, that the jury could not have been influenced by it. It follows that the trial court prejudicially erred.
Reversed and remanded.
SMITH, J., concurs. DOWD, J., dissents in separate opinion.. For a host of decisions on this principle see 24 B, C.J.S., Criminal Law, § 1915(2), n. 86.
. The principle was applied in State v. Banton, 342 Mo. 45, 111 S.W.2d 516[4-5] (1937), in reversing a conviction because the prosecutor erroneously told the jury over objections that the defendant had taken a change of venue.