Neve, Inc., Appellant, vs. Joseph J. Jerkovich, Respondent.

may not be cited except as provided by

Minn. Stat. §480 A. 08, subd. 3 (1996).

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 C8-98-766

State of Minnesota,

Respondent,

vs.

Jeffrey Raymond Foster,

Appellant.

 Filed January 5, 1999

 Affirmed in part, reversed in part, and remanded

 Anderson, Judge

Kanabec County District Court

File No. K19767

Michael A. Hatch, Attorney General, Robert A. Stanich, Assistant Attorney General, Cynthia K. Schneider, Certified Student Attorney, 1400 NCL Tower, 445 Minnesota Street, St. Paul, MN 55101; and

Norman J. Loren, Kanabec County Attorney, 19 North Vine Street, Mora, MN 55051 (for respondent)

John M. Stuart, State Public Defender, Susan K. Maki, Assistant Public Defender, 2829 University Avenue Southeast, Suite 600, Minneapolis, MN 55414 (for appellant)

Jeffrey R. Foster, MCF- Willow River/Moose Lake, 1001 Lakeshore Drive, Moose Lake, MN 55767-9449 (appellant pro se)

Considered and decided by Shumaker, Presiding Judge, Kalitowski, Judge, and Anderson, Judge.

 U N P U B L I S H E D O P I N I O N

 ANDERSON, Judge

Appellant challenges his sentence for separate convictions of first-degree criminal sexual conduct and raises additional challenges to his convictions. Although the evidence supports the jury's verdict, appellant's conviction for the single-incident count was a lesser-included offense of the multiple-incident count requiring that we affirm in part, reverse in part, and remand.

 FACTS

Appellant Jeffrey Foster began living with S.W. and her mother in 1990 and married S.W.'s mother in 1996. At trial, S.W. testified that, from the spring of 1994, when she was 13, until the fall of 1996, when she was 16, appellant had sexual intercourse with her about 15 times. She testified in detail about several of these incidents. Appellant denied ever sexually abusing his stepdaughter. The jury convicted appellant of two counts of criminal sexual conduct in the first degree.

The district court sentenced appellant to concurrent prison terms of 86 and 110 months and a 10-year period of conditional release.

 D E C I S I O N

In his pro se brief, appellant also challenges his conviction arguing insufficient evidence and other errors at trial. An appeal challenging the sufficiency of the evidence requires appellate review of the record in a light most favorable to the jury's verdict. State v. Webb, 440 N.W.2d 426, 430 (Minn. 1989). Viewing the evidence in favor of the jury's verdict, the testimony of S.W. was sufficient to support appellant's conviction. Appellant claims the evidence was insufficient because there was no physical evidence such as DNA or semen linking him to the crimes. But corroboration is not required. See Minn. Stat. § 609.347, subd. 1 (1996) (prosecution under section 609.342 does not require corroboration of victim's testimony). Apparently, the jury found S.W.'s testimony convincing, even without corroboration. See State v. Moore, 438 N.W.2d 101, 108 (Minn. 1989) (assuming jury believed state's witnesses); see also State v. Bliss, 457 N.W.2d 385, 390 (Minn. 1990) (leaving credibility determinations to jury).

Appellant also argues he should have been able to introduce evidence that S.W. had been a victim in another incident of sexual abuse. Minn. Stat. § 609.347, subd. 3 (1996), generally prohibits evidence of a victim's prior sexual conduct. Such evidence is admissible

only if the probative value of the evidence is not substantially outweighed by its inflammatory or prejudicial nature and [then] only in the circumstances set out in paragraphs (a) and (b).

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(a) When consent of the victim is a defense in the case.

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(b) When the prosecution's case includes evidence of semen, pregnancy, or disease at the time of the incident or, in the case of pregnancy, between the time of the incident and trial * * * .

 Id. Neither of the circumstances in (a) or (b) applied to this case and, accordingly, the district court correctly excluded the evidence. Evidence of S.W.'s prior sexual abuse was not admissible to show a predisposition to fabricate charges. See State v. Caswell, 320 N.W.2d 417, 419 (Minn. 1982) (holding evidence of prior false accusation of rape admissible). Appellant does not allege that S.W.'s earlier accusation was false. Instead, appellant wanted to introduce the evidence to show that S.W. "knew all the tricks to get me out of her life."

Appellant also argues generally that he should have been able to introduce evidence to prove that S.W. is a liar. But there is no record that appellant's counsel attempted to introduce the evidence that appellant says was erroneously excluded. Because these evidentiary issues were not raised in the district court, they are waived on appeal. See Roby v. State, 547 N.W.2d 354, 357 (Minn. 1996) (failure to raise issues before trial court precludes litigation on appeal). Alternatively, under Minn. R. Evid. 608(b), extrinsic evidence of a specific instance of conduct is inadmissible to show a witness is untruthful. The type of evidence that appellant claims was excluded, a police officer's testimony establishing an incident where S.W. stole some items and lied about it and S.W.'s social service records to establish incidents where she lied, are inadmissible under rule 608. See id.

Appellant also challenges the fairness of the jury. He argues that a juror who had an outstanding arrest warrant should not have been allowed to serve. Also, appellant claims he realized after trial that one of the jurors had at one time thrown him off his land and claims this juror might have remembered that incident and been biased against appellant. Again, appellant waived these challenges by failing to challenge the jurors at trial. See Roby, 547 N.W.2d at 357. Alternatively, appellant does not establish prejudice as a result of the selection of these jurors. See State v. Stufflebean, 329 N.W.2d 314, 317 (Minn. 1983) (to reverse conviction based on juror bias requires showing that juror was challenged for cause, that actual prejudice resulted from failure to dismiss, and appropriate objection was made by appellant).

Appellant argues, and respondent agrees, that he was erroneously convicted of and sentenced for an included offense. Appellant was charged with violating Minn. Stat. § 609.342, subd. 1(g) (1996) (Count 1), and § 609.342, subd. 1(h)(iii) (1996) (Count 2). The elements of the two crimes are the same except that subdivision 1(g) is for a single incident and subdivision 1(h)(iii) requires multiple incidents. See Minn. Stat. § 609.342, subd. 1 (1996). Both convictions were based on appellant's conduct from the spring of 1994 to the fall of 1996.

Upon prosecution for a crime, the actor may be convicted of either the crime charged or an included offense, but not both. An included offense may be

* * * *

(4) A crime necessarily proved if the crime charged were proved.

Minn. Stat. § 609.04, subd. 1 (1996). Because proof of multiple acts of sexual abuse between the spring of 1994 and the fall of 1996 necessarily proved a single act within the same time frame, subdivision 1(g) was an included offense of subdivision 1(h)(iii).

When a defendant is convicted of more than one charge for the same conduct, a court may impose sentence on only one count. State v. LaTourelle, 343 N.W.2d 277, 284 (Minn. 1984). Appellant's sentence for violating Minn. Stat. § 609.342, subd. 1(g), must be vacated. Id.

Appellant also argues that his period of conditional release should be five years. Minn. Stat. § 609.346, subd. 5 (1996), requires a five-year conditional release for persons convicted of a criminal sexual offense and a ten-year conditional release for persons convicted a second or subsequent time. "A previous sex offense conviction" means a criminal sexual conduct conviction entered "before the commission of the present offense of conviction." Minn. Stat. § 609.346, subd. 3 (1996). Appellant had no conviction prior to committing his current offense. Accordingly, his conditional release term should be five years.

 Affirmed in part, reversed in part, and remanded.