Dixie A. Linn appeals from a district court order which affirmed her conviction for driving under the influence of alcohol, third offense. On appeal, Linn alleges that the State failed to prove a valid judgment for purposes of enhancement because one of the convictions used by the State was not signed *333by the county court judge. We affirm for three separate reasons detailed hereinafter.
FACTUAL SUMMARY
On December 12, 1993, Dixie A. Linn, who was represented by counsel, entered a guilty plea to the charge of driving under the influence of alcohol. The county court accepted Linn’s plea, and an enhancement hearing was held that same day. At the outset of the enhancement hearing, the county court made the following statement to Linn:
Now, you have certain rights in an enhancement hearing and that includes the rights to review the record of that prior, of those prior convictions. You have the right to object to the validity of those prior convictions, then you have the right to present mitigating circumstances to the court regarding those prior convictions, prior to sentencing occurring in this case, and among other things, I’ll have to be convinced that you were represented by counsel or that you had knowingly, voluntarily, and intelligently waived your right to counsel at the time of those prior convictions.
At the enhancement hearing, the State introduced evidence of two prior convictions for driving under the influence of alcohol. Exhibit 1 is a certified copy of the record of a conviction of October 2, 1992, for driving under the influence of alcohol, second offense.
Exhibit 2 is a certified copy of the record of a conviction for driving under the influence of alcohol, second offense, for which Linn was sentenced on July 9, 1992. Exhibit 2 contains a complaint and a two-page journal entry. The journal entry was not signed by a county court judge. Exhibit 2 bears the seal of the county court for Hall County, is certified as a true copy of the original on file with the court, and is signed by the court clerk.
Both exhibits 1 and 2 reflect that Linn was represented by counsel. The exhibits were received in evidence without objection from Linn’s counsel. Immediately thereafter, the trial judge observed, “Exhibit two does not reflect the signature of a county judge on the journal entry. All right, with no argument *334and objection by either side the court will find that this is a third offense, driving under the influence of alcohol.”
The county court then found Linn guilty of driving under the influence of alcohol, third offense. Linn returned to court on January 6, 1994, and was sentenced to pay a $500 fine, court costs, and the breath testing fee. She was also sentenced to 3 months’ incarceration, and her driver’s license was revoked for 15 years. Linn appealed to the district court for Hall County, which affirmed the decision of the county court. This appeal timely followed.
ASSIGNMENT OF ERROR
On appeal to this court, Linn alleges that the State failed to prove a valid judgment because the journal entry in exhibit 2 was not signed by a county court judge.
STANDARD OF REVIEW
In reviewing decisions of the district court which affirm, reverse, or modify decisions of the county court, a higher appellate court will consider only those errors specifically assigned in the appeal to the district court and again assigned as error in the appeal to the higher appellate court. See, State v. Gerstner, 244 Neb. 508, 507 N.W.2d 490 (1993); State v. Erlewine, 234 Neb. 855, 452 N.W.2d 764 (1990). The record shows that Linn filed a statement of errors in the county court which raised the issue of sufficiency of the evidence used for enhancement. Thus, the assigned error is properly before us.
ANALYSIS
Linn argues that the State failed to prove that she was guilty of driving under the influence of alcohol, third offense. If a person has been convicted in the previous 8 years of operating or being in actual physical control of any motor vehicle while under the influence of alcoholic liquor or drugs, the convictions may be used to enhance the penalty for a current conviction. See Neb. Rev. Stat. § 60-6,196 (Reissue 1993).
In a proceeding to enhance the sentence because of prior convictions, the State has the burden to prove such prior convictions. State v. Ristau, 245 Neb. 52, 511 N.W.2d 83 (1994). When using a prior conviction to enhance a sentence, *335the State need only show that at the time of the prior conviction the defendant had, or waived, counsel. Id. In LeGrand v. State, ante p. 300, 527 N.W.2d 203 (1995), this court applied two recent U.S. Supreme Court cases, Custis v. U.S., _ U.S. _, 114 S. Ct. 1732, 128 L. Ed. 2d 517 (1994), and Nichols v. U.S., _ U.S. _, 114 S. Ct. 1921, 128 L. Ed. 2d 745 (1994), which provide further support for this holding. In fact, LeGrand holds that the only permissible ground of attack on a prior conviction being used for enhancement purposes is that the transcript fails to disclose whether the defendant had or waived counsel at the time the plea was entered. There is no claim that either of Linn’s prior two convictions were uncounseled, and in fact the exhibits involved herein show that she had counsel for both convictions.
A judicial record of this state, or of any other federal court of the United States, may be proved by the producing of the original, or by a copy thereof, certified by the clerk or the person having the legal custody thereof, authenticated by his seal of office, if he have one.
Neb. Rev. Stat. § 25-1285 (Reissue 1989). See State v. Ziemba, 216 Neb. 612, 346 N.W.2d 208 (1984). The statute says nothing about the signature of the judge being part of the proof of the judicial record.
In compliance with § 25-1285, the State proved with certified copies Linn’s prior convictions for driving under the influence of alcohol. Linn argues that although exhibit 2 is a certified copy of her July 9, 1992, conviction, the State failed to prove that a valid judgment existed because exhibit 2 was not signed by the county court judge rendering the judgment of conviction. Linn’s argument appears to be that a valid final judgment is not rendered until and unless a judge’s signature appears thereupon. Although we believe the attack which Linn attempts here on her prior conviction goes beyond that allowable in an enhancement proceeding, we also disagree with her that the lack of a judge’s signature means that the State did not carry its burden of proof with respect to prior convictions.
Rendition of judgment occurs when the court makes an oral pronouncement and accompanies that pronouncement with a notation on the trial docket. Neb. Rev. Stat. § 25-1301 (Reissue *3361989). Failing a notation on the trial docket, a judgment is rendered when some written notation of the judgment is filed in the records of the court. In re Interest of J.A., 244 Neb. 919, 510 N.W.2d 68 (1994). In a criminal case, it is the sentence which is the judgment. State v. Spotted Elk, 227 Neb. 869, 420 N.W.2d 707 (1988).
The issue of the validity of an unsigned judgment has been previously addressed by the Nebraska Supreme Court. In Stacks v. Crawford, 63 Neb. 662, 88 N.W. 852 (1902), the court found that a transcript of the district court of the United States was competent evidence, even though the presiding judge failed to sign the journal of the record.
In In re Application of Niklaus, Niklaus v. Holloway, 144 Neb. 503, 13 N.W.2d 655 (1944), the appellant attacked the validity of a judgment because the judge failed to sign the journal entry. The Nebraska Supreme Court stated, “The failure of a judge to sign the judgment does not have the effect of rendering the judgment invalid.” Id. at 511, 13 N.W.2d at 659. While signing judgments is a prudent practice for trial courts, the failure of the judge to sign the judgment does not render the judgment invalid when an authenticated copy thereof is offered into evidence for the sole purpose of enhancing the penalty on a later conviction.
Additionally, notwithstanding that the judgment in exhibit 2 was not signed, Linn failed to object to its admission. If a defendant fails to object to the admission in evidence of his or her prior convictions, error claimed with respect to the admission of that evidence is not preserved for appellate review. State v. Tonge, 217 Neb. 747, 350 N.W.2d 571 (1984); State v. Penas, 200 Neb. 387, 263 N.W.2d 835 (1978). Failure to assert a timely objection at the time of trial constitutes a waiver of the objection. State v. Red Kettle, 239 Neb. 317, 476 N.W.2d 220 (1991).
The county court advised Linn of her rights in the enhancement hearing prior to the admission of the exhibits, including the right to object to the validity of her prior convictions. Linn was given the opportunity to challenge her prior convictions, and she failed to do so. After the exhibits had been received in evidence, the court pointed out that exhibit 2 *337had not been signed by the county court judge, yet Linn offered no objection. Linn waived the right to object to the validity of her prior convictions. Linn’s assignment of error is without merit.
CONCLUSION
We find that the failure of the presiding judge to sign the judgment in exhibit 2 did not render it invalid. Moreover, Linn waived any objection to the validity of her prior convictions. Finally, Linn’s attack on exhibit 2 exceeds the permissible boundaries for attacks on prior convictions being used solely for enhancement purposes. For these reasons, we affirm the judgment of the district court which affirmed the judgment of the county court.
Affirmed.