W. W. LESSLEY, District Judge,
sitting in place of Mr. Justice Sheehy, delivered the opinion of the Court.
Defendant appeals from his conviction of the crime of sexual intercourse without consent following a jury trial in the District Court of Yellowstone County.
Defendant is the stepfather of the victim, who was thirteen years old at the time of the incident. The specific incident with which defendant was charged occurred on or about January 27, 1977. At trial the victim testified to the following sequence of events.
On January 25, or 26, the victim had been left in charge of the family home in Huntley, Montana, and of her younger brother and sister while her mother attended a conference in California, and defendant, her stepfather, was working out of the state.
On the night of the specific acts charged, the victim and her brother and sister had gone to bed for the night. Sometime between 9 and 10 pm., defendant arrived home, awakened the victim, and asked her to cook something to eat for him. The victim, wearing an ankle length nightgown, complied.
Sometime later, after defendant had finished eating and the victim had returned to bed, defendant began calling to the victim, asking her to get up and come sit beside him on the couch in the living room. The victim again got out of bed and returned to the kitchen where she cleared away the dirty dishes. While she was so engaged, defendant went back to his bedroom and began looking for something. He then called the victim back to his room to look at something.
The victim went back to the doorway of defendant’s bedroom. He asked her to sit beside him on the bed, which she refused to do. Shortly thereafter, he grabbed her by her wrist and pulled her [265]*265down on the bed beside him. After laying there awhile, defendant got up, procured a pornographic magazine from his desk drawer and attempted to force the victim to look at it.
Defendant then shut the bedroom door, turned out the lights, removed his pants, pushed the victim’s nightgown to her waist, removed her underpants, and attempted unsuccessfully to have genital sexual intercourse. After some period of time, defendant, failing to achieve sexual penetration, grabbed the victim by the back of the neck and forced her to take his penis into her mouth. He held her in this position until he ejaculated.
The victim was then allowed to go to the bathroom where she cleaned up and, after turning off the television, she returned to her own bed. Because there was nothing on the television, the victim estimated the time as being at least after midnight.
At school the next day, the victim called her aunt in Billings to come pick her up. The aunt, upon arriving at the school, was generally informed by two of the victim’s schoolmates that she had been sexually assaulted by her stepfather. Thinking that they meant the victim had been raped, the aunt, after calling the victim’s mother in California, took her for a pelvic examination which revealed no sign of semen, trauma, or penetration. The examining physician did not, however, examine the victim’s mouth.
The next day, the victim’s mother returned to Billings and along with the victim went to the Yellowstone County sheriff’s department to report the incident. With the mother’s consent, a search warrant was obtained and executed for the seizure of the bedspread from defendant’s bed, the victim’s nightgown, some towels and the pornographic magazine.
Shortly after the execution of the search warrant, defendant was . arrested and taken to the Yellowstone County jail where several pubic hairs and his undershorts were taken. The bedspread, nightgown, towels and undershorts were sent to the FBI laboratory in Washington, D.C., for testing along with samples of pubic hair from both defendant and the victim.
At trial the victim further testified, over the continuing objection [266]*266of defense counsel, that defendant had previously committed sexual offenses against her similar to the offense with which he was charged. The victim testified that these acts had begun three years earlier while the family lived in Wisconsin and all occurred when she and defendant were alone. In total, the victim testified that she had been forced to have oral sex with defendant between ten and thirty times prior to the January 27 incident. None of the victim’s testimony as to these prior acts were corroborated by other testimony or evidence.
The State presented further testimony from the FBI agents who conducted the examination of the physical evidence. These agents testified that a spermatozoa stain was discovered on the bedspread and on the defendant’s undershorts, but they were unable to identify these stains in any more detail. No stains were found on either the nightgown or the towels. As it developed at trial, however, it appears that the wrong nightgown had been seized and the one the victim had been wearing at the time of the incident was inadvertently washed before the error was discovered.
The physician who examined the victim after the incident testified as to the absence of any evidence of semen, trauma, or penetration in the pelvic area. He conceded that he had not examined her mouth.
Defendant testified in his own behalf, denying any and all of the sexual assaults alleged by the victim. Further, the defense attempted to impeach the victim’s testimony regarding prior assaults by bringing out that although she had had numerous opportunities to do so, she had never reported any of the prior' incidents to anyone.
The issues before us are:
1. Whether the District Court erred in allowing the victim to testify over defendant’s objection to uncharged, uncorroborated prior acts of sexual crimes allegedly committed upon her by the defendant?
2. Whether the District Court erred in refusing defendant’s of[267]*267fered cautionary instruction on use of the prosecuting witness’s testimony?
3. Whether the evidence produced at trial can sustain the verdict as a matter of law?
Defendant in his argument below and before this Court recognizes the exception to the general rule of the incompetency of evidence of the commission of other crimes for which a defendant is not charged. That exception, which is the rule in this jurisdiction, is of ancient lineage. Simply put, the evidence of prior sexual acts by a defendant and a prosecutrix is admissible in a trial for a sexual offense.
In this first issue of his appeal, defendant challenges as “illogical” one of the oldest and most often applied general rules and exception, in this Satte’s criminal jurisprudence. This general rule as well as the exception were recently summarized in State v. LaVe (1977), 174 Mont. 401, 571 P.2d 97, 100:
“Generally, evidence of other offenses or of other similar acts at other times is inadmissible for the purpose of showing the commission of the particular criminal offense charged. State v. Taylor, 163 Mont. 106, 120, 515 P.2d 695 (1973). The reason is that the defendant is entitled to be informed of the offense charge so that he need prepare his defense only to that particular offense. Proof of other offenses subjects him to surprise and to a defense of multiple collateral or unrelated issues. State v. Jensen, 153 Mont. 233, 455 P.2d 631 (1969). This rule applies to evidence of other offenses regardless of whether defendant was actually charged with the other offense. See, State v. Tiedemann, 139 Mont. 237, 362 P.2d 529 (1961).
“The general rule, however, is subject to several exceptions when such evidence becomes admissible: (1) When similar acts with the same prosecuting witness are involved; (2) when similar acts are not too remote in time; and (3) when evidence of other offenses tends to establish a common scheme, plan or system, where such other offenses are similar to, closely connected with and not too remote from the one charged, and where they are so that the proof [268]*268of one tends to establish the other. State v. Taylor, supra; State v. Jensen, supra.”
Accord, State v. Heine (1975), 169 Mont. 25, 27-28, 544 P.2d 1212, 1213; State v. Taylor (1973), 163 Mont. 106, 120-22, 515 P.2d 695, 703-04; State v. Frates (1972), 160 Mont. 431, 436-37, 503 P.2d 47, 50; State v. Jensen (1969), 153 Mont. 233, 238-39, 455 P.2d 631, 633-34; State v. Merritt (1960), 138 Mont. 546, 548-50, 357 P.2d 683, 684; State v. Sauter (1951), 125 Mont. 109, 111-16, 232 P.2d 731, 731-34; State v. Gaimos (1916), 53 Mont. 118, 124, 162 P. 596, 599; State v. Peres (1903), 27 Mont. 358, 360, 71 P. 162, 163.
The above rules and exception have also recently been coddified in Rule 404(b), Mont.R.Evid.:
(b) Other crimes, wrongs, acts. Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show that he acted in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident.”
As noted in the Commission Comment to this section, the Commission intended “that there be no change in the admissibility of such evidence under existing Montana law.”
Montana has given protection to the defendant in such a case as this against the admission of potentially prejudicial evidence of other crimes or wrongful acts. It is the rule that both trial courts and this Court are obligated to balance carefully the relative probative value of the evidence of other offenses against the prejudice inherent in this type of evidence in light of the actual need to introduce such evidence. State v. Skinner (1973), 163 Mont. 58, 64, 515 P.2d 81, 84; State v. Frates, 160 Mont. at 437, 503 P.2d at 50.
Rule 403, Mont.R.Evid., requires the exclusion of otherwise relevant evidence “. . . if its probative value is substantially outweighed by the danger of unfair prejudice . . .”
There emerges a four element test to determine the admissibility [269]*269of evidence of other crimes or acts criminal prosecutions such as the one here. The first three of these elements were identified in State v. Jensen, 153 Mont. at 239, 455 P.2d at 634; the fourth is based on Rule 403, Mont.R.Evid. The four factors are:
1. The similarity of crimes or acts;
2. nearness in time; and
3. tendency to establish a common scheme, plan or system; and
4. the probative value of the evidence is not substantially outweighed by the prejudice to the defendant.
Applying this test to the facts of the instant appeal, we conclude that the evidence of defendant’s other acts against the victim was properly admitted. First, all of the prior acts were sexual in nature, in almost all instances involving exactly the type of sexual contact charged against defendant, and always involving the same victim.
The prior sexual acts testified by the prosecutrix have a similarity of inherent probability. In Wisconsin, defendant arranged to be at home when the prosecutrix returned from school and no one else was there; in Hays, defendant stayed home while his wife was gone. There is the hand of a plan with an ulterior motive carrying out an intent by scheme and design of the defendant that was a resultant common course of conduct.
Second, the earliest act testified to by the victim occurred three years before the act resulting in the criminal charges. The remaining acts apparently occurred on a “regular” basis as opportunity afforded until the January 27, 1977, incident. While the act of three years before is close to the limit as being too remote for probative value, see State v. Nicks (1958), 134 Mont. 341, 343, 332 P.2d 904 905, when placed in the total sequence of events, it clearly forms an integral part. In any event, we have specifically held admissible testimony of similar acts occurring over a three-year period of time. State v. Heine, 169 Mont. at 28, 544 P.2d at 1214; State v. Jensen, 153 Mont. at 239, 455 P.2d at 634.
Third, all of the acts testified to occurred between the defendant and the victim; all transpired when the two were alone; and all in[270]*270volved essentially identical behavior on the part of the defendant. As stated in Jensen:
“In this case the other acts proved show a continuous pattern of behavior on the part of the defendant for a period of over 3 years. The pattern during that period remained virtually the same. This is precisely what is meant by common scheme, plan or system.” 153 Mont. at 239, 455 P.2d at 634.
The facts of the instant appeal likewise illustrate a common scheme, plan or system.
The fourth factor is perhaps the most difficult to apply. Evidence of other acts, especially of the nature testified to in this case, invariably will result in prejudice to the defendant to a certain degree. Nevertheless, when the victim will testify to such a concerted and continuous course of offensive conduct as apparently transpired between the defendant and victim here, and will thereafter be subject to cross-examination on that testimony, we cannot say as a matter of law that the probative value of the evidence was substantially outweighed by the prejudice to defendant.
Defendant does not challenge the applicability of this exception, but insists that in the instant case the prior uncharged offenses are uncorroborated testimony of the prosecutrix.
Defendant relies on People v. Stanley (1967), 67 Cal.2d 812, 63 Cal.Rptr. 825, 433 P.2d 913. That case is clearly distinguishable.
In Stanley, the California Court held the only purpose of the testimony of previously charged sex offenses was to corroborate the prosecuting witness’s testimony. The Court held under the facts of that case the testimony was insufficient to so corroborate.
Stanley is further distinguishable from the case before us on appeal. The victim here was not shown to have a bad reputation for veracity, nor was she contradicted on any material point in her testimony. More important, the evidence of defendant’s prior acts was not introduced to corroborate the victim’s testimony as to the charged offense; in sex offense cases in Montana, the victim’s testimony does not need to be corroborated. State v. Metcalf [271]*271(1969), 153 Mont. 369, 378, 457 P.2d 453, 458; State v. Gaimos, 53 Mont. at 126, 162 P. at 599.
Further, the purpose of the evidence under attack on this appeal was offered to show “plan, motive, scheme, design, a common course of conduct... .” This purpose was stated during the trial by the county attorney:
“We would offer this testimony as an exclusion from the hearsay rule in that it goes to plan, motive, scheme, design, a common course of conduct, a single transaction involving a series of incidents with the same Defendant and the same victim who was always available to him.”
Even Stanley, upon which appellant relies, recognizes this use:
“There are, of course, certain situations in which evidence of other crimes is admissible. In cases involving sex crimes, it has been held that evidence of other not too remote sex offenses with the prosecuting witness is admissible to show a lewd disposition or the intent of defendant towards the prosecuting witness. (People v. Sylvia, 54 Cal.2d 115, 119-120, 4 Cal.Rptr. 509, 351 P.2d 781; see People v. Kelley, 66 Cal.2d 232, 234, 57 Cal.Rptr. 363, 424 P.2d 947).
“Defendant does not dispute the latter rule as a general proposition . . .” 63 Cal.Rptr. at 827-828, 433 P.2d at 915-16.
The admission of this testimony was not error. Defendant’s first issue is then without merit.
We are concerned, nevertheless, with the possibility that the exceptions we have discussed thus far may “swallow up” the general rule; that is, that by asserting that the purpose of the testimony is to establish a common scheme of recent similar behavior, the State may be able to circumvent the general rule altogether, resulting in, perhaps, prejudice difficult to measure to the defendant. As we have stated:
“The general rule should be strictly enforced in all cases where applicable, because of the prejudicial effect and injustice of such evidence, and should not be departed from except under conditions [272]*272which clearly justify such a departure. The exceptions should be carefully limited, and their number and scope not increased.” State v. Tiedemann (1961), 139 Mont. 237, 242-43, 362 P.2d 529, 531.
Accord, State v. Sauter, 125 Mont. at 116, 232 P.2d at 734.
It was perhaps such a similar concern which motivated the Minnesota Supreme Court to adopt the following procedures in the admission of evidence of other crimes:
“2. As an additional safeguard in the trial of future cases, but without retroactive application in so far as the rules are new, the following procedures shall be followed:
“(a) Evidence of other crimes may not be received unless there has been notice as required by State v. Spreigl, 272 Minn. 488, 496, 139 N.W.2d 167, 173. (Applicable to all cases tried after December 17, 1965).
‘(b) At the time the evidence is offered, the prosecutor shall specify the exception to the general exclusionary rule under which it is admissible.
“(c) If the evidence of other crimes is received for purposes of identity rather than to show a common scheme or plan, there must nevertheless be some relationship in time, location, or modus operandi between the crime charged and the other offenses.
“(d) Evidence of other crimes is admissible only if the trial court finds the direct or circumstantial evidence of defendant’s identity is otherwise weak or inadequate, and that it is necessary to support the state’s burden of proof. It should be excluded where it is merely cumulative and a subterfuge for impugning defendant’s character or for indicating to the jury that he is a proper candidate for punishment.
“(e) The evidence of defendant’s participation in other crimes need not be proved beyond a reasonable doubt but must be clear and convincing.
“(f) Both at the time the evidence is received and in the final charge, the court should admonish the jury that the testimony is received for the limited purpose of establishing identity. It is the [273]*273court’s duty to advise the jury in unequivocal language that defendant is not being tried and may not be convicted for any offense except that charged, warning them that to convict for other offenses may result in unjust double punishment.” State v. Billstrom (1967), 276 Minn. 174, 149 N.W.2d 281, 284-85.
Many of these procedural steps have either direct or analogous support in Montana’s cases or statutes. Steps (c) and (d) are broadly included in the general rule and exceptions we have discussed above. Step (e) is logically derived from general principles of law. The evidence of the other acts is not for purposes of proving other crimes; defendant will not be penalized for the other offenses unless they are specifically charged and proved. Therefore, the burden of proof as to the acts need not rise to the level required in a criminal prosecution for those acts.
As to step (a), we discussed the question of notice to the defendant that evidence of prior acts may be used against him in State v. Nicks, 134 Mont. at 343-44, 332 P.2d at 905:
“The reason for excluding such evidence is of course fundamental. The defendant should be informed by the information of the particular crime with which he is charged. He looks to the information to ascertain the charge that he must be prepared to meet. If he may be subjected to evidence of his conduct many years before the time named in the information he will be taken by surprise and the ‘issues would be multiplied indefinitely, without previous notice to the defendant, and greatly to the distraction of the jury.’ Quen Guey v. State, 20 Ariz. 363, 181 P. 175, 177.”
See also, State v. Jensen, 153 Mont. at 238, 455 P.2d at 633-34.
Analogously, the State is required by statute to specifically inform a defendant of its intent to present evidence of prior felony convictions in seeking increased penalties under the persistent felony offenders statute. Section 46-18-503 MCA. A defendant who may have to refute evidence of past acts or offenses, not specifically charged, should be accorded the same notice. Included in such notice should be a statement of the exception under which this [274]*274evidence is sought to be admitted as required by step (b) of the Minnesota procedures.
As to step (f), the duty of the trial court to specifically instruct the jury as to the purposes for which the evidence of other offenses has been received has been mentioned in several of our cases. E. g., State v. Heine,, 169 Mont. at 28, 544 P.2d at 1214; State v. Harris (1915), 51 Mont. 496, 499, 502, 154 P. 198, 199, 200; State v. Vinn (1914), 50 Mont. 27, 37, 144 P. 773, 776-77.
We feel these procedures should be standardized in cases of this type and therefore hold that the following procedures shall be followed without retroactive application insofar as they are new:
(a) Evidence of other crimes may not be received unless there has been notice to the defendant that such evidence is to be introduced. The procedures set forth in section 46-18-503 MCA should serve as guidelines for the form and content of such notice. Additionally, the notice to the defendant shall include a statement as to the purposes for which such evidence is to be admitted.
(b) At the time of the introduction of such evidence, the trial court shall explain to the jury the purpose of such evidence and shall admonish it to weigh the evidence only for such purposes.
(c) In its final charge, the court should instruct the jury in unequivocal terms that such evidence was received only for the limited purposes earlier stated and that the defendant is not being tried and may not be convicted for any offense except that charged, warning them that to convict for other offenses may result in unjust double punishment.
The foregoing procedures are not intended to change any of the other rules governing the admission of this evidence discussed earlier.
We consider the next claimed error, the refusal of defendant’s proposed cautionary instruction. The fundamental question presented is the credibility of witnesses. The proposed cautionary instruction reads as follows:
“You are instructed that charges such as the one made against [275]*275the defendant in this case are easy to make and hard to defend against even by one who is guiltless; and where the State relies upon the uncorroborated testimony of the prosecutrix, you, the jury, should be cautioned of convicting upon such evidence. The reason is that from motives as various as human perversity, the charge may be made when no offense at all had been done, or it may be made against an innocent person when the crime has, in fact, been committed.”
Instructions similar to the one above were offered in the earlier cases of State v. Keeler (1916), 52 Mont. 205, 211, 156 P. 1080, 1081, and State v. Mihalovich (1924), 69 Mont. 579, 585, 222 P. 695, 697. In each of those cases, this Court held that the trial judge’s refusal to give the instruction was proper when there was nothing in the record to suggest that the prosecutrix was motivated by private malice or a desire for revenge. See State v. Boe (1963), 143 Mont. 141, 148-49, 388 P.2d 372, 376. The test for determining the propriety of giving an instruction such as that offered by defendant was set forth in the recent case of State v. Ballew (1975), 166 Mont. 270, 276, 532 P.2d 407, 411:
“. . . it is clear that refusals] to give such an instruction will be error only when some specific cause is shown for distrusting the testimony of the complaining witness. Such causes might include manifest malice, desire for revenge, or an absence of corroborating evidence tending to support the facts testified to by the complaining witness.”
Defendant points out nothing in the record which would indicate any malice or desire for revenge as a motivation for the testimony of the prosecuting witness. Furthermore, although there is no legal requirement that the testimony of the prosecutrix be corroborated, State v. Metcalf (1969), 153 Mont. 369, 378, 457 P.2d 453, 458, corroborative evidence was in fact presented during trial. As stated earlier, the pornographic book which the prosecutrix testified had been shown to her by defendant was recovered during the search of defendant’s home and introduced into evidence. Sperm and defendant’s pubic hair were found on the bedspread on which the offense occurred.
[276]*276This Court has indicated in earlier cases that the propriety of giving an instruction such as that offered by defendant is doubtful in any case. See State v. Peterson (1936), 102 Mont. 495, 502, 59 P.2d 61, 64; State v. Mihalovich, 69 Mont. at 585, 222 P. at 697. The refusal to give such an instruction constitutes error, if at all, only in the limited circumstances set forth in Ballew. Because none of those circumstances existed in this case, the trial court did not err in refusing to caution the jury as to the use of the-testimony of the prosecuting witness.
There was sufficient instruction to properly guide the jury in the field of credibility of witnesses. Court’s Instruction No. 2 provided:
“Every witness is presumed to speak the truth. This presumption, however, may be repelled by the manner in which he testified, by the character of his testimony, or by evidence affecting his reputation for truth, honesty integrity, or his motives or by contradictory evidence.”
People v. Rincon-Pineda (1975), 14 Cal.3d 864, 123 Cal.Rptr. 119, 538 P.2d 247, speaks against the use of such cautionary instruction in these words:
“As we observed, Sir Matthew Hale himself was convinced that the best test of the credibility of a prosecutrix was the surrounding circumstances, including any corroborating evidence, of a particular case. Moreover, Hale affirmed the ‘excellency’ of leaving the question of credibility to the jury.” 123 Cal.Rptr. at 128, 538 P.2d at 256.
The Court conclusively speaks against the use in these words:
“We now turn to the question whether the instruction may be given discretionarily by a trial court. Having already noted the fundamental differences in the position of the defendant before the bar of modern American justice as opposed to the English prisoner’s dock of 300 years ago, and having dispensed with the notion that those accused of sex offenses suffer any special prejudice today, we think the instruction as it has customarily been worded (i. e., CALJIC No. 10.22) is inappropriate in any context, and the further use of such language is hereby disapproved. (Accord, State [277]*277v. Feddersen (Iowa 1975) 230 N.W.2d 510, 514.)” 123 Cal.Rptr. at 132, 538 P.2d at 260.
The Court acted properly in refusing the cautionary instruction.
In considering defendant’s finál issue we find that the court was correct in denying defendant’s motions to dismiss. Section 46-16-403 MCA provides:
“When, at the close of the state’s evidence or at the close of all the evidence, the evidence is insufficient to support a finding or verdict of guilty, the court may, on its own motion or on the motion of the defendant, dismiss the action and discharge the defendant.”
In State v. Yoss (1965), 146 Mont. 508, 514, 409 P.2d 452, 455, this Court stated that a directed verdict of acquittal is appropriate in criminal cases “only where the State fails to prove its case and there is no evidence upon which a jury could base its verdict.” Accord, State v. Thompson (1978), 176 Mont. 150, 576 P.2d 1105, 1108. The decision whether to dismiss the charge or direct a verdict of acquittal lies within the sound discretion of the trial court and will be disturbed on appeal only when abuse is shown. State v. Buckley (1976), 171 Mont. 238, 243, 557 P.2d 283, 285-86.
In Montana, convictions for sexual intercourse without consent may be based on the uncorroborated testimony of the prosecuting witness. State v. Metcalf (1969), 153 Mont. 369, 378, 457 P.2d 453, 458. See, State v. Paddock (1930), 86 Mont. 569, 575, 284 P. 549, 551. In State v. Gaimos (1916), 53 Mont. 118, 126, 162 P. 596, 599, this Court stated:
“Only in those rare cases where the story told is so inherently improbable or is so nullified by material self-contradictions that no fair-minded person could believe it may we say that no firm foundation exists for the verdict based upon it.”
Contrary to defendant’s assertion in this case, it is not “inherently improbable” that the other small children in the family of the prosecutrix, who were eight and nine years old, should sleep through the incident as described by the prosecutrix. Because the testimony was not materially self-contradictory or improbable, it [278]*278provided a sufficient basis as a matter of law for a verdict of guilty.
Under such circumstances, the trial judge properly denied defendant’s motion to dismiss, leaving the weighing of testimony and the assessment of the credibility of the witnesses to the jury. State v. Buckley, 171 Mont. at 243, 557 P.2d at 286.
We find no error. The judgment of conviction is affirmed.
MR. CHIEF JUSTICE HASWELL and JUSTICES DALY and HARRISON concur.
MR. JUSTICE SHEA dissents.