
642 P.2d 1079 (1982)
The STATE of Montana, Plaintiff and Respondent,
v.
Elaine GOLTZ, Defendant and Appellant.
No. 81-267.
Supreme Court of Montana.
Submitted January 12, 1982.
Decided April 1, 1982.
*1080 Mark Bauer argued, Great Falls, for defendant and appellant.
Mike Greely, Atty. Gen., Helena, J. Fred Bourdeau, County Atty., Great Falls, Carroll Blend, Deputy County Atty., argued, Great Falls, for plaintiff and respondent.
WEBER, Justice.
Defendant appeals from a conviction of felony theft following jury trial in the Eighth Judicial District Court, Cascade County. We affirm the District Court.
Defendant presents the following issues for review:
(1) Whether the District Court erred in denying defendant's motion to dismiss based upon an eighteen month pre-indictment delay.
(2) Whether the District Court erroneously allowed into evidence certain "uncorroborated admissions" by defendant.
(3) Whether the District Court erroneously instructed the jury in such a way as to shift the burden of proof to defendant.
(4) Whether the District Court erred in denying defendant's motion for a directed verdict of acquittal for failure of the State to prove its case beyond a reasonable doubt.
Defendant managed the Don Plaza Motel in Great Falls from July 1978 through January 1979. She was paid $800.00 per month or 16% of the take, whichever was more, and she had free use of an apartment in the motel. Early in her employment, her employer advanced defendant $3,200 so that she could pay certain pressing debts. Defendant's husband, a construction worker, was temporarily laid off in November.
Defendant's daily duties included registering guests, preparing individual registration cards, and keeping a log of charges accrued, expenditures made and motel receipts (cash, checks, and credit card charge slips). Approximately once a week defendant transferred the daily records and receipts to the bookkeeper, a local high school student, who prepared bank deposit slips, deposited receipts in the Don Plaza bank account, and reconciled motel records and the motel bank account. The bookkeeper made seven deposits to the Don Plaza account in October.
Defendant offered to and did take over the bookkeeping during the bookkeeper's vacation in November. Bank records show only one deposit in November, on the 13th, covering receipts up to November 6, 1978. The next deposit, covering receipts after November 27, 1978, was made by the regular bookkeeper on December 5, 1978. There are no deposits for the period from November 7 through November 26, although an audit of the motel's books revealed over $5,000 in receipts for that period.
The discrepancy between motel receipts and bank deposits was not discovered until January, 1979, when the employers were *1081 notified that the Don Plaza bank account was overdrawn. An investigation revealed that defendant had filled out three bank deposit record slips, and turned them over to the bookkeeper, unaccompanied by bank receipts. She told the bookkeeper she had misplaced the bank receipts, but later admitted that she had never made the deposits, but had only prepared phony deposit slips. When defendant's employers confronted her in January about the overdraft, she told them she had deposited the money in her checking account. She wrote her employers two checks upon her account to cover the missing receipts; both checks were returned for insufficient funds.
Defendant has consistently maintained that one of the bags containing receipts was taken from her office, and the network of lies was intended only to protect her job until she could obtain money from her father to cover the loss. Her father never covered the loss, and he did not testify at trial.
In March of 1979, the County Attorney received the evidence upon which he based the subsequent prosecution. A delay of eighteen months followed, during which time the State was attempting to audit the motel books, track down travelers' checks, and investigate by mail. Defendant was charged with felony theft, by information on September 15, 1980, and arrested on October 23, 1980. Defendant's motion to dismiss for delay in prosecution was denied, and trial commenced on January 23, 1981. From a jury verdict of guilty, defendant appeals to this Court.

I.
Defendant argues that she was denied her right to a speedy trial by the eighteen month pre-indictment delay. She relies upon Barker v. Wingo (1972), 407 U.S. 514, 92 S.Ct. 2182, 33 L.Ed.2d 101, and its numerous progeny in Montana; State v. Larson (1981), Mont., 623 P.2d 954, 38 St.Rep. 213; State v. Cassidy (1978), 176 Mont. 385, 578 P.2d 735; State v. Keller (1976), 170 Mont. 372, 553 P.2d 1013, to name a few. Defendant also argues that prosecutorial delay may justify reversal on a due process basis, as having prejudiced defendant's right to a fair trial. She relies upon United States v. Marion (1971), 404 U.S. 307, 92 S.Ct. 455, 30 L.Ed.2d 468; United States v. Lovasco (1977), 431 U.S. 783, 97 S.Ct. 2044, 52 L.Ed.2d 752; and State v. Burtchett (1974), 165 Mont. 280, 530 P.2d 471.
Defendant's reliance upon the line of speedy trial cases arising under the Sixth Amendment is misplaced. Marion and Lovasco both clearly indicate that speedy trial guarantees do not extend to the period prior to formal accusation or arrest.
"In United States v. Marion, 404 U.S. 307, 92 S.Ct. 455, 30 L.Ed.2d 468 (1971), this Court considered the significance, for constitutional purposes, of a lengthy preindictment delay. We held that as far as the Speedy Trial Clause of the Sixth Amendment is concerned, such delay is wholly irrelevant, since our analysis of the language, history, and purposes of the Clause persuaded us that only `a formal indictment or information or else the actual restraints imposed by arrest and holding to answer a criminal charge ... engage the particular protections' of that provision. Id., at 320, 92 S.Ct. at 463. We went on to note that statutes of limitations, which provide predictable, legislatively enacted limits on prosecutorial delay, provide `"the primary guarantee, against bringing overly stale criminal charges."' Id., at 322, 92 S.Ct. at 464, quoting United States v. Ewell, 383 U.S. 116, 122, 86 S.Ct. 773, 777, 15 L.Ed.2d 627 (1966)." United States v. Lovasco, 431 U.S. at 788-789, 97 S.Ct. at 2048, 52 L.Ed.2d at 758.
Cf. United States v. Mills (9th Cir.1981), 641 F.2d 785, 787; State v. Larson, Mont., 623 P.2d at 957-958, 38 St.Rep. at 215.
Both Marion and Lovasco, however, indicate that the statute of limitations is not a defendant's only protection against pre-indictment delay.
"... [T]he Due Process Clause has a limited role to play in protecting against oppressive delay." United States v. Lovasco, 431 U.S. at 789, 97 S.Ct. at 2048, 52 L.Ed.2d at 758.

*1082 "... [T]he Due Process Clause of the Fifth Amendment [and, here, the Fourteenth Amendment] would require dismissal of the indictment if it were shown at trial that the pre-indictment delay in this case caused substantial prejudice to [defendant's] rights to a fair trial and that the delay was an intentional device to gain tactical advantage over the accused." United States v. Marion, 404 U.S. at 324, 92 S.Ct. at 465, 30 L.Ed.2d at 481.
Cf. United States v. Cederquist (9th Cir.1981), 641 F.2d 1347, 1351; United States v. Mills, 641 F.2d at 788; United States v. Krasn (9th Cir.1980), 614 F.2d 1229, 1235; United States v. West (9th Cir.1979), 607 F.2d 300, 304-305.
Those Ninth Circuit decisions addressing pre-indictment delay, subsequent to Marion and Lovasco, have established that the burden of proof is on the defendant and the prejudice alleged cannot be merely speculative. In West, the Ninth Circuit Court of Appeals stated:
"The crucial element in the due process test established by Mays [United States v. Mays (9th Cir.1977), 549 F.2d 670] is the finding of actual prejudice to the defendants. Satisfaction of this element is a prerequisite to finding a due process violation. United States v. Titus, 576 F.2d 210, 211 (9th Cir.1978) [cert. denied, 439 U.S. 860, 99 S.Ct. 180, 58 L.Ed.2d 169]; Arnold v. McCarthy, 566 F.2d 1377, 1382 (9th Cir.1978). If the prejudice is allegedly due to the loss of a witness, the defendant `must show not only the loss of the witness and/or evidence but also [must] demonstrate how that loss is prejudicial to him.' United States v. Mays, supra at 677. Such proof must be definite and not speculative and `[t]he assertion that a missing witness might have been useful does not show the "actual prejudice" required by Marion.' Id. at 677 ..." United States v. West, 607 F.2d at 304.
This Court addressed the matter of preindictment delay in State v. Burtchett, supra, and added a wrinkle to the standards established in Marion, and later in the federal courts.
"... [T]here is no question but that a delay in time between the commission of an offense and the commencement of the prosecution, by the filing of an information, termed `preindictment delay' can be the denial of due process. [citing Marion.] Mere delay, in and of itself, is not sufficient. There must be either actual prejudice to the conduct of the defense, or that the State intentionally delayed to gain some tactical advantage over appellant, or to harass him. United States v. Marion, supra." State v. Burtchett, 165 Mont. at 283, 530 P.2d at 473. (Emphasis added.)
Defendant now argues that the "either/or" language in Burtchett clearly indicates that this Court intended that a due process violation could be found without defendant's having to prove both improper intent and actual prejudice. The State argues that the Burtchett language was a mere "lapsus linguae," and this Court should now rule that both improper intent and actual prejudice must be found.
We find that defendant neither asserted and proved the State's improper intent nor proved actual prejudice resulting from the delay; therefore, the difference between the Burtchett standard and the Marion standard is not determinative here.
Defendant claims that because of the pre-indictment delay, she lost the testimony of one "key witness for the defense" and a number of unnamed Don Plaza employees who might have indicated the guilt of someone other than defendant. Defendant has failed to indicate the nature of the lost testimony and how it might be exculpatory. Such speculation is insufficient to establish actual prejudice. See United States v. West, 607 F.2d at 304-305; United States v. Mays, 549 F.2d at 677. Defendant claims the record shows that witnesses for the State were unable to remember certain details such as the exact dates of vacations or which employer confronted the defendant first. Defendant, again, has made no *1083 effort to show how those particular memory lapses impaired her defense. Indeed, the facts themselves were not disputed. Defendant never claimed that she had deposited the motel receipts or that she did not make out phony bank receipts, that she did not falsely tell her employers she had deposited the receipts in her own account, or that she had not written bad checks to "repay" her employers. Defendant erroneously concludes that proof of some failure of memory is automatically proof of prejudice. In United States v. Mills, 641 F.2d at 789, the Ninth Circuit Court of Appeals stated:
"Nor does the claim that the witnesses' memories have dimmed without proof of impairment constitute actual prejudice. United States v. Rogers, 639 F.2d 438 (8th Cir.1981); Mays, supra."

There is no evidence that defendant's position was in any way impaired by failure of the State's witnesses to recall certain details.
Defendant mentions only one specific instance of her own memory failure from which some prejudice may flow. She claimed, during cross-examination, that she had never been paid more than $800.00 per month at the Don Plaza. The State produced a cancelled check to defendant for over $900.00. Defendant claims she forgot that paycheck in the two years between the offense and trial, and that being contradicted before the jury severely damaged her credibility. We do not find this single instance sufficient to mandate reversal of conviction. The contradiction was on a minor point not directly related to those actions of defendant which led to her conviction.
Finally, in United States v. Lovasco, 431 U.S. at 795-796, 97 S.Ct. at 2051, 52 L.Ed.2d at 762-763, the United States Supreme Court stated:
"In our view, investigative delay is fundamentally unlike delay undertaken by the Government solely `to gain tactical advantage over the accused,' United States v. Marion, 404 U.S., at 324, 92 S.Ct., at 465, precisely because investigative delay is not so one-sided. Rather than deviating from elementary standards of `fair play and decency,' a prosecutor abides by them if he refuses to seek indictments until he is completely satisfied that he should prosecute and will be able promptly to establish guilt beyond a reasonable doubt. Penalizing prosecutors who defer action for these reasons would subordinate the goal of `orderly expedition' to that of `mere speed,' Smith v. United States, 360 U.S. 1, 10, 79 S.Ct. 991, 997, 3 L.Ed.2d 1041 (1959). This the Due Process Clause does not require. We therefore hold that to prosecute a defendant following investigative delay does not deprive him of due process, even if his defense might have been somewhat prejudiced by the lapse of time." (Emphasis added.)
There is ample evidence that the delay in this case resulted from continuing investigation by the State, e.g., its attempt to track down credit card charge slips and travelers checks. There was no error in the District Court's denial of defendant's motion to dismiss due to delay.

II.
Defendant maintains that the District Court erred by allowing into evidence her employer's testimony that defendant had falsely assured them the money had been deposited for them into defendant's personal checking account. Defendant concedes she has no hearsay objection, but argues that the statements to her employers were inadmissible because they were "uncorroborated admissions" and could never be corroborated because they were untrue.
We do not accept defendant's rather ingenious argument, for the simple reason that her statements were not admissions. They were "false exculpatory statements," which are admissible.
"False exculpatory statements by a party may be used not only to impeach, but also to prove consciousness of guilt and unlawful intent. Williamson v. United States, 310 F.2d 192, 199 (9th Cir.1962). See DeVore v. United States, 368 F.2d 396, 397 (9th Cir. 1966); 2 Wigmore on Evidence § 278(2) (3rd ed. 1940) [supp. *1084 1981]." United States v. Pistante (9th Cir. 1971), 453 F.2d 412, 413.
Cf. Burden Young v. United States (9th Cir.1966), 358 F.2d 429, 431, wherein the Circuit Court of Appeals held, that admission into evidence of false exculpatory statements made by defendant to an F.B.I. agent was not error "whatever ground may have been relied on by the court."
An "admission" is defined as "an avowal or acknowledgement of a fact or of circumstances from which, together with other facts, guilt may be inferred." 22 C.J.S. Criminal Law § 730(a). Ordinarily it is not the fact of the avowal but its substance, i.e., that some act was in fact done, which allows an inference of guilt. Here, it is not the substance of the avowal, but the fact that the avowal was false that allows an inference of guilt.
We hold that the statements in question were not admissions, but false exculpatory statements, and, as such, were properly admitted by the trial court.

III.
Defendant argues that the trial court erred in its instructions to the jury. The trial court instructed the jury that:
"Purpose or knowledge are manifested by the circumstances connected with the offense. Purpose or knowledge need not be proved by direct evidence, but may be inferred from acts, conduct and circumstances appearing in evidence." (Other instructions indicated that an omission could constitute an act.)
Defendant objected to the instruction as being "very close to a Sandstrom type of instruction." (Sandstrom v. Montana (1979), 442 U.S. 510, 99 S.Ct. 2450, 61 L.Ed.2d 39.) The trial court refused defendant's proposed instruction that it is not the act alone, but the criminal intention together with the act, that makes the actor guilty. Defendant did not offer an instruction defining "inference," nor did she suggest that such an instruction be given. Defendant now argues that, without such an instruction, the effect of the instructions, taken as a whole, was to "shift the burden to the defendant to show that her failure to deposit the funds of the Don Plaza Motel was not coupled with the purpose to deprive the owners of those funds." Such a shift of burden runs afoul of Sandstrom, according to defendant.
We disagree. In the first place, defendant cannot on appeal hold the State or the trial court responsible for their failure to include an instruction defining "inference," when she herself did not offer or request such an instruction.
"...[I]f defendant felt further instructions, including more specific instructions were necessary, it was incumbent upon him to request more specific instructions. No such request appears in the record." State v. Bretz (1979), Mont., 605 P.2d 974, 998, 36 St.Rep. 1037, 1067, cert. denied, 444 U.S. 994, 100 S.Ct. 529, 62 L.Ed.2d 425.
Furthermore, the jury was adequately instructed that the State must prove each element of the offense charged. The instructions separated the several elements of the offense and clearly indicated that the State must prove "beyond a reasonable doubt to a moral certainty" that (1) defendant's purpose was to deprive the owners of their property, and (2) defendant purposely or knowingly obtained or exerted unauthorized control over the cash, checks and credit card charge slips. Finally, since the Sandstrom decision was reversed in the United States Supreme Court in 1979, this Court has been inundated by appeals attempting to equate "must presume" with "may infer," and thus bring the instructions on permissive inference as to intent within the Sandstrom ban. We have indicated that no such equation will be accepted. In State v. Bad Horse (1980), Mont., 605 P.2d 1113, 1120, 37 St.Rep. 45, 54, this Court cited State v. Coleman (on rehearing) (1979), Mont., 605 P.2d 1000, 1054, 36 St.Rep. 2237, 2241:
"The holding in Sandstrom is not to be construed to mean that whenever a trial court instructs the jury that it may resort to inference to determine subjective matters such as knowledge or purpose, that *1085 thereby the State has been relieved of its burden of proof. The United States Supreme Court did not intend such limitation, and we do not find any such intention in the language of Sandstrom or its related cases. The jury was not allowed to rest solely upon the permitted inference in the Coleman case, but under the instruction had to require such an inference to meet the standard as beyond a reasonable doubt."
The disputed instruction here was not mandatory; the instructions as a whole adequately informed the jury. We find no shift of the burden of proof to the defendant. No error.

IV.
The fourth and final allegation of error raised by defendant is that the trial court improperly denied her motion for a directed verdict of acquittal. Defendant argues that the State failed to eliminate the "reasonable possibility" that someone else stole the receipts, and also failed to prove that defendant exerted unauthorized control over the receipts; therefore, no reasonable juror could find all elements of the crime were proven beyond a reasonable doubt.
This Court addressed the question of a directed verdict of acquittal in State v. Smith (1980), Mont., 609 P.2d 696, 698, 37 St.Rep. 583, 586:
"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 ...'
"The general rule in Montana appears to be 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.' State v. Yoss (1965), 146 Mont. 508, 409 P.2d 452, 455. `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. Just (1979), Mont., 602 P.2d 957, 965, 36 St.Rep. 1649."
And in State v. Pendergrass (1980), Mont., 615 P.2d 201, 205, 37 St.Rep. 1370, 1375, we stated:
"... This Court remains ever mindful of one fundamental rule  that questions of fact must be determined solely by the jury, and that given a certain legal minimum of evidence, this Court on review will not substitute its judgment for that of the jury ... State v. Merseal (1975), 167 Mont. 412, 415, 538 P.2d 1366, 1367-1368."
Pendergrass and Merseal also indicate that the test of evidence sufficient to warrant a directed verdict of acquittal is the same as the test of sufficiency of evidence on appeal, i.e., whether, viewing the evidence in the light most favorable to the State, substantial evidence exists to support a verdict of guilty. The State presented evidence showing that defendant handled both the motel receipts and the bank records during the period for which receipts are missing; that she prepared phony bank deposit records, and built a framework of easily-discovered lies around her failure to deposit the receipts; that she had a history of indebtedness; that her husband was unemployed in November of 1978. Both motive and opportunity were established by the evidence; together with the evidence of defendant's evasive behavior, there was more than adequate support for a guilty verdict.
Affirmed.
DALY, HARRISON, SHEA and MORRISON, JJ., concur.
