This case began with the filing of a two-count indictment against appellant charging violations of 18 U.S.C. §§ 912 and 913, respectively. Appellant was found not guilty on Count II, the Section 913 count, but was found guilty on Count I, the Section 912 count, of falsely pretending to be an F.B.I. agent and, in such pretended character, demanding a 1961 Oldsmobile from one Moore, as charged, in the indictment.1 Upon such finding judgment was entered and this appeal followed.
Fierson’s defense at trial was that he did in fact repossess the automobile over which Moore, the conditional buyer, was exercising control, but he steadfastly denied that he did so while pretending to be an F.B.I. agent. Fierson at no time disputed the character of the act charged.2 He disputed only the allegation that he committed it.
Over objection, the government, during its case in chief, for the stated purpose of proving willfulness and intent, elicited the testimony of one Goethceus who recounted that eleven months prior to the date of the instant offense, Fier-son had demanded the former’s automobile while representing himself (Fier-son) as an F.B.I. agent.3 An appropriate limiting instruction on this evidence was given by the court and the jury, in final instruction, was charged that an intent to defraud was an essential element of the offense charged in Count I of the indictment.4 Fierson urges that *1022the introduction of Goethceus’ testimony was reversible error. We agree.
As a general rule, evidence of prior criminal acts of an accused, which are not charged in the indictment or information, is inadmissible. Boyd v. United States, 142 U.S. 450, 12 S.Ct. 292, 35 L.Ed. 1077 (1892); United States v. Menk, 406 F.2d 124 (7th Cir. 1969); United States v. Reed, 376 F.2d 226 (7th Cir. 1967); United States v. Silvers, 374 F.2d 828 (7th Cir. 1967); United States v. White, 355 F.2d 909 (7th Cir. 1966); United States v. Magee, 261 F.2d 609 (7th Cir. 1958). More precisely, evidence of the commission of prior criminal acts is not competent to prove that the accused committed the act charged in the indictment or information. This rule reflects a firmly rooted notion of our jurisprudence — a man ought not be convicted of doing a specific bad act because he is a bad fellow generally. The rule is but a specific instance of the wider prohibition against allowing the prosecution to first put character in issue. McCormick, Evidence § 157 (1954).5
This rule of exclusion, however, is not universal. Evidence of prior criminal acts may be admissible on other contested issues. Thus enter the “exceptions.” The government here relied on a well-founded “exception” — introduction to show intent and willfulness; to negate innocence due to mistake, misadventure, or similar folly. United States v. Marine, 413 F.2d 214 (7th Cir. 1969); Gilstrap v. United States, 389 F.2d 6 (5th Cir. 1968); United States v. Klein, 340 F.2d 547 (2d Cir. 1965); Whaley v. United States, 324 F.2d 356 (9th Cir. 1963), cert. denied, 376 U.S. 911, 84 S.Ct. 665, 11 L.Ed.2d 609, rehearing denied 376 U.S. 966, 844 S.Ct. 1122, 11 L.Ed.2d 984 (1964); Rule 4-04(b), Proposed Rules of Evidence for the United States District Courts and Magistrates (March 1969 Preliminary Draft). The only question here is whether the “exception” was properly wed to the facts of this case. We find that it was not.
Admissibility of this type of evidence is subject to knowable, yet necessarily, imprecise standards. At its roots the problem is one of balancing probative value against prejudice. Roe v. United States, 316 F.2d 617 (5th Cir. 1963). The question is, in the first instance, left to the sound discretion of the trial judge who can readily measure the pulse of the proceedings. Glasser v. United States, 315 U.S. 60, 62 S.Ct. 457, 86 L.Ed. 680 (1942); Gilstrap v. United States, supra; United States v. Byrd, 352 F.2d 570 (2d Cir. 1965); United States v. Klein, supra; Whaley v. United States, supra. The term “discretion” means only that no hard and fast rules are laid down. It does not mean that the trial court’s decision is immune from review.
In order to be admissible as bearing upon wilfulness and intent, evidence that the accused has committed prior criminal acts must first be shown to be similar to the offense charged and close enough in time to be relevant. In this case, the reported previous criminal act was identical in type to the offense charged, and on the question of proximity in time, we cannot say that the passage of eleven months from the date of the prior criminal act to the date of the offense alleged in the indictment was, in itself, sufficient to require exclusion. See Whaley v. United States, supra.
More than this, however, is required. Obviously intent must be an element of the offense to justify the admission of this type of evidence. Prior criminal acts cannot be proved to show intent when intent is not an element of the of*1023fense charged. United States v. Menk, supra. Equally obvious is the fact that when intent is a material element of the offense, it is part of the prosecuting attorney’s case to be proved in chief lest he find himself out of court at the close of his evidence.
However, to justify admission into evidence of an accused’s prior criminal acts to establish willfulness and intent, it is necessary that willfulness and intent be more than merely formal issues in the sense that the defendant is entitled to an instruction thereon. See United States v. Magee, supra. When, as in this case, the government has ample evidence to take the case to the trier of fact for its deliberation, a plea of not guilty cannot, by itself, be construed as raising such a keen dispute on the issue of willfulness and intent so as to justify admission of this type of evidence. See United States v. Magee, supra.
The facts of this case, as developed at trial, did not raise even the slightest suggestion that Fierson did the physical act charged but without the requisite willfulness and intent.6 There was no suggestion of accident or mistake. The defendant simply said he did not commit the physical act charged. When the government had adduced evidence that the defendant repossessed Moore’s car while pretending to be an F.B.I. agent, its case was made out. If the defendant had admitted the above acts but defended on the theory that he was joking and really did not mean it, then the matter of his intent might be said to be in issue and the Goethceus testimony could have been offered to negate the suggestion of mistake. But here the issue of willfulness and intent was not sharpened; it was not really in dispute.7 Goethceus’ testimony was purely cumulative on the issue for which it was introduced. It seems obvious that the government sought to prove that the defendant here probably did tell Moore that he was an F.B.I. agent by the evidence that he made a similar statement, under similar circumstances, to Goethceus some eleven months earlier.
Admission of this evidence was, under settled standards, error. United States v. Byrd, supra; United States v. Klein, supra; United States v. Magee, supra. It was reversible error because the trial below was to a jury.8
We hold that it is reversible error in a jury trial of an accused charged with pretending to be an F.B.I. agent and demanding an automobile from another in violation of 18 U.S.C. § 912, to allow the government, during its case in chief, to introduce evidence of a prior criminal act of the accused in order to show willfulness and intent when, as here, the accused does not, except for demanding an instruction on the requisite willfulness and intent, otherwise put that issue in dispute.
Reversed and remanded for a new trial.
. Count I of the indictment charged a violation of 18 U.S.C. § 912, which reads as follows:
Whoever falsely assumes or pretends to be an officer or employee acting under the authority of the United States or any department, agency or office thereof, and [1] acts as such, or [2] in such pretended character demands or obtains any money, paper, document or thing of value, shall be fined not more than $1,000 or imprisoned not more than three years, or both.
(Brackets added to distinguish the two separate offenses contained therein.)
. This statement is subject to one qualification. Dpring his case, Fierson called James Manahan, a former assistant United States Attorney for the Southern District of Indiana, and asked inter alia, whether Manahan’s investigation of the Goethceus incident, see Note 3, infra, and accompanying text, reflected “an intent or no intent on the part of Mr. Fier-son.” The government’s timely objection thereto was sustained.
. Formal charges against appellant stemming from this earlier incident had been dismissed on the government’s motion.
. The authorities are divided on the question of whether an intent to defraud is an essential element of the offense charged in Count I. Compare, Honea v. United States, 344 F.2d 798 (5th Cir. 1965) and United States v. Harth, 280 F.Supp. 425 (W.D.Okla.1968) with United States v. Guthrie, 387 F.2d 569 (4th Cir. 1967) and United States v. Meeker, 110 F.Supp. 743, 14 Alaska 249 (D.Alas.1953). Since *1022the kind of intent required to commit the offense charged in Count I of the indictment is not an issue before us, we express no opinion on the correctness of this instruction to the jury.
. This prohibition is carried forward in Rule 4-04(a), Proposed Rules of Evidence for the United States District Courts and Magistrates (March 1969 Preliminary Draft).
. Indeed, Fierson’s one attempt to put the issue of willfulness and intent into issue proved abortive. See Note 2, supra.
. This is the critical element which readily distinguishes this case from United States v. Marine, supra, which held that evidence of prior criminal acts similar to those charged was admissible to prove intent where the defendant disputed the issue of knowledge and specific intent was an essential element of the crime charged.
. In Menk this court refused to reverse a conviction resulting from a court trial where evidence of prior criminal acts was erroneously admitted because:
a trained, experienced Federal District Court judge * * * must be presumed to have exercised the proper discretion in distinguishing between the improper and the proper evidence introduced at trial, and to have based his decision only on the latter * * *. Menk, supra, 406 F.2d at 127.
That decision was careful to point out, however, that “if this had been a jury trial we would be compelled to reverse.” Menk, supra, at 126.