Appellant seeks reversal of his conviction for armed bank robbery in violation of 18 U.S.C. § 2113(a). He contends that (1) certain evidence should be suppressed because of inadequacies in the affidavit supporting the search warrant, (2) a shoeprint from the scene of the crime should have been excluded, (3) certain remarks of the prosecutor constituted improper comment on appellant's failure to take the stand, and (4) his prior conviction should have been determined to be inadmissible under Federal Rule of Evidence 609(a)(1). We agree only with the last contention and reverse on that ground. Because a new trial is likely, it is appropriate that we explicitly rule on the appellant's remaining contentions. We conclude that none is meritorious.

The robbery occurred at the United California Bank, Tower Branch, in Fresno, California on March 9, 1979, by two masked robbers who escaped in a stationwagon owned and driven by Melba New with whom the appellant lived prior to the robbery. Shortly before the robbery, the appellant was seen with New in Chowchilla, California, driving a primer-colored Camaro. Several hours after the robbery New was arrested in her stationwagon which contained masks, shoes, and a gun similar to those used by the robbers. Appellant was linked to the robbery when his fingerprints were found on the car, hair similar to his was found on one of the masks, and his short and stocky build was found to match that of one of the robbers.

Ten days after the robbery, on March 19, 1979, appellant was arrested in Oregon in a primer-colored Camaro. On the basis of an affidavit set forth in the margin1 a warrant to search the Camaro was obtained. The search revealed bait bills from the robbery and a pair of size 51/2 shoes. Appellant was arrested and at that time denied having been in Fresno on the day of the robbery.

At the trial an impression of a shoeprint left at the scene of the robbery, which was lifted by a police technician using a fingerprint lifting technique, was introduced in evidence. A qualified expert expressed the opinion that the shoeprint was made by a shoe that was found in New's car and was the same size as the shoe found in appellant's Camaro. New testified that the shoes in her car belonged to her or her son.

Appellant did not take the stand following a ruling by the trial court that his prior conviction for armed robbery could be used to impeach his credibility. He sought to preserve his right to have the trial court's decision reviewed by establishing on the record his intention to take the stand if his prior conviction were excluded and outlining the nature of his testimony to enable the trial court to apply Rule 609(a)(1). See United States v. Cook, 608 F.2d 1175, 1186 (9th Cir. 1979). Appellant offered to testify that the bait money found in his car was given to him by New, information that New herself refused to supply.

During the trial the prosecutor, commenting on the ownership of the shoes found in New's car, stated that "you've not heard testimony that they are not Kenneth Hendershot's." Appellant objected to this observation as improper under the Fifth Amendment. The prosecutor apologized and a curative instruction was promptly given by the trial court.

On the basis of the record before us, we hold that appellant successfully preserved his right to have the trial court's ruling reviewed under principles we announced in United States v. Cook. Appellant's showing was sufficient to enable the trial court to comply with the weighing process Rule 609(a)(1) requires. Application of Cook to the facts of this case involves no retroactivity inasmuch as appellant's trial occurred subsequent to June 29, 1979, the date Cook was filed.

Turning to the merits, we hold that it was error for the trial court to rule that the appellant's prior felony conviction for armed robbery could be used for impeachment purposes if appellant took the stand. We reach this conclusion because it is not clear that the trial court properly applied Rule 609(a)(1), which requires that the prosecution bear the burden of establishing that the probative value of admitting a prior conviction for a crime not involving "dishonesty or false statement" outweighs its prejudicial effect to the defendant. Instead of articulately striking a balance between probative value and prejudice as Rule 609(a)(1) requires, the record suggests the possibility that the trial court believed no such balance was required in the absence of a showing by the appellant that the prejudice "far outweighed" the prior conviction's probative value. This possibility arises because of the prosecution's reliance on Gordon v. United States, 127 U.S.App.D.C. 343, 383 F.2d 936 (D.C.Cir.1967). Gordon, in explaining Luck v. United States, 121 U.S.App.D.C. 151, 348 F.2d 763 (D.C.Cir.1965), observed that the burden of persuasion was on the accused to show that the prejudice to him from the admission of prior convictions for impeachment purposes far outweighed its probative value. 127 U.S.App.D.C. at 346, 383 F.2d at 939. Counsel for appellant did not acquiesce in the prosecution's use of Gordon; rather, he pointed specifically to Rule 609(a)(1) and correctly asserted that exclusion was appropriate when "the prejudicial effect of the prior condiction (sic) would outweigh its probative value." The trial court gave no indication of what standard it was employing; it merely ruled that the prior conviction would be admissible.2

As indicated, Rule 609(a)(1) placed the burden of persuasion on the prosecutor, and admission is conditioned upon probative value outweighing prejudice. Although we have recognized that the balancing required by Rule 609(a)(1) constitutes an exercise of the trial court's discretion which should be overturned only upon a showing of an abuse, United States v. Cook, 608 F.2d 1175 (9th Cir. 1979), this case must be resolved differently because of the possibility that the trial court applied the improper legal standard of Gordon. Under these circumstances, we are unable to say that the trial court did not abuse its discretion.

Once more, as in Cook, we recognize that serious crimes, other than those of "dishonesty or false statement," are admissible, provided the trial court exercises its discretion to so admit them in accordance with the principles of Rule 609(a)(1). United States v. Cook, 608 F.2d 1175, at 1187, 1979. The proviso is important. Although appellate courts should not overturn evidentiary rulings of trial courts based on the proper exercise of their discretion, it is a primary obligation of appellate courts to insist that this discretion be exercised within the applicable framework of legal rules. In some instances this framework may impose no standard at all or none other than good faith and the avoidance of arbitrariness. In others it is more restrictive. The framework of Rule 609(a)(1) is one of the latter. Congress, after much debate, created a framework in which, with respect to a defendant, the burden of persuasion is placed upon the prosecution and a particular process of weighing is required. Both we and the trial courts must respect that decision.

Appellant argues that the affidavit set forth above is insufficient because (1) it did not show that it was more likely than not that the evidence sought would be in the car as opposed to appellant's house, (2) it did not contain sufficient detail to enable the magistrate to evaluate independently the reliability of the hearsay statement that appellant was seen in the Camaro before and after the crime, and (3) it contained a misrepresentation that allowed the magistrate to infer that the Camaro was used in the robbery. None of these contentions has merit.

First, the "more-likely-than-not" standard is improper. It is only necessary that the affidavit enable the magistrate to conclude that it would be reasonable to seek the evidence in the place indicated by the affidavit. United States v. Melvin, 596 F.2d 492, 495 (1st Cir. 1979); see also United States v. Brown, 455 F.2d 1201, 1203 (9th Cir.), cert. denied, 406 U.S. 960, 92 S. Ct. 2069, 32 L. Ed. 2d 347 (1972); Porter v. United States, 335 F.2d 602, 604 (9th Cir. 1964); United States v. Lucarz, 430 F.2d 1051 (9th Cir. 1970). The affidavit conforms to this standard. Nor is a conclusion of the affiant, "(b) ased on my experience from prior bank robbery investigations," improper. It is not necessary to detail that experience to determine that the conclusion is not capricious. See Jaben v. United States, 381 U.S. 214, 224-25, 85 S. Ct. 1365, 14 L. Ed. 2d 345 (1965); see also United States v. Dubrofsky, 581 F.2d 208, 212-13 (9th Cir. 1978).

The hearsay statement "that one and one half hours before the robbery took place, Kenneth Alvin Hendershott (sic) was seen in possession of a 1967 to 1970 Chevrolet Camaro, rust primer in color," was sufficiently supported to permit independent evaluation by the magistrate. Support consisted of facts that appellant was arrested while in the Camaro, that he admitted he owned the Camaro, and that his build matched that of one of the robbers.

Finally, appellant argues that the affidavit permits the inference that the Camaro was used in the robbery and that such inference is a misrepresentation. There are two answers to this. The first is that the inference is not a compelling one. The affidavit is consistent with what the fact appear to have been, viz., that the Camaro was used both before and after, but not in connection with, the robbery. The second is that appellant has failed to show that the misrepresentation was intentional or reckless and that it was prejudicial. See Franks v. Delaware, 438 U.S. 154, 98 S. Ct. 2674, 57 L. Ed. 2d 667 (1978).

Appellant's objection to the admissibility of the shoeprint is based essentially on the contention that lifting shoeprints by fingerprint lifting techniques is not sufficiently accepted by crime technicians generally to justify its admissibility. See United States v. Amaral, 488 F.2d 1148, 1153 (9th Cir. 1973); accord, United States v. Brown, 557 F.2d 541, 556 (6th Cir. 1977). The technician who lifted the shoeprint was well qualified to employ the fingerprint technique and he testified that it had been used for shoeprints by Santa Clara and Fresno technicians and that it is taught as a shoeprint lifting technique at a Modesto crime scene investigation course. This is enough to make the shoeprint admissible in the absence of any evidence discrediting the lifting technique. No discrediting evidence was offered by the appellant. Cf. United States v. Kilgus, 571 F.2d 508, 510 (9th Cir. 1978) (unrebutted testimony of defendant's expert witness that technique for identifying flying aircraft was not generally accepted among scientific community rendered testimony based on that technique inadmissible).

The prosecutor's comment was ill advised but any Griffin error was harmless beyond a reasonable doubt. Griffin v. California, 380 U.S. 609, 85 S. Ct. 1229, 14 L. Ed. 2d 106 (1965); see also Chapman v. California, 386 U.S. 18, 87 S. Ct. 824, 17 L. Ed. 2d 705 (1967). The promptly given curative instruction negated the improper inference that the prosecutor's comment made possible.

Reversed and Remanded.