State of Minnesota, Respondent, vs. Omar Kwabena Walford, Appellant.

may not be cited except as provided by

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

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 C7-98-970

State of Minnesota,

Respondent,

vs.

Lonnie Dean Melland,

Appellant.

 Filed December 22, 1998

Affirmed

Harten, Judge

Anoka County District Court

File No. T6-98-4407

Lonnie D. Melland, 1344 Brookdale Drive, Brooklyn Park, MN 55444 (appellant pro se)

Hubert H. Humphrey, III, Attorney General, 14th Floor NCL Tower, 445 Minnesota Street, St. Paul, MN 55101 (for respondent)

Anne Spencer Tretinyak, Sweeney, Borer & Sweeney, 386 North Wabasha, Suite 1200, St. Paul, MN 55102 (for respondent)

Considered and decided by Peterson, Presiding Judge, Schumacher, Judge, and Harten, Judge.

 U N P U B L I S H E D O P I N I O N

 HARTEN, Judge

Appellant Lonnie Dean Melland challenges his petty misdemeanor speeding conviction, arguing that the district court's failure to grant his application for a subpoena resulted in prejudicial error. We affirm.

 FACTS

On January 27, 1998, Officer Ben Johnson of the Blaine Police Department determined by radar that Melland was driving on Highway 65 near 107th Avenue at a speed of 67 miles per hour (mph). After stopping Melland's vehicle, Johnson issued Melland a citation for traveling 67 mph in a 55 mph speed zone. Johnson testified that the speed limit was posted as 55 mph just north of 99th Avenue, around 102nd Avenue, and just north of 105th Avenue.

Melland appeared pro se and submitted a pre-trial application to the district court for authority to subpoena an employee of the Minnesota Department of Transportation (DOT). Where the application form requested the applicant to indicate the relevance of the testimony sought, Melland noted, "accuracy of documents." The district court denied Melland's subpoena request, stating that Melland had to show why the documents were relevant to his petty misdemeanor court trial.

Before the presentation of testimony at trial, Melland stated:

I'd like to stipulate that we really don't even have to have the officer testify as to the radar; training, qualifications, whatnot. I am not contesting that at all.

When the district court asked Melland whether he agreed that he was traveling 67 mph, Melland answered, "It's possible. I am going to stand by my statement on the police report that says I was going just over 60 miles an hour."

In his defense, Melland attempted to introduce DOT documents purportedly showing that the speed limit on the relevant stretch of Highway 65 was not posted on January 27, 1998 and, therefore, was 65 mph as required by Minn. Stat. § 169.14, subd. 2 (a) (2) (Supp. 1997). The Blaine City Attorney objected on hearsay grounds to the introduction of these documents. Because the documents were not certified and the DOT employee was not present to authenticate them, the district court excluded the DOT documents as inadmissible hearsay. The district court convicted Melland of speeding. Melland appeals.

 D E C I S I O N

Melland challenges the district court's denial of authorization to subpoena the DOT employee, arguing that the district court thereby precluded him from presenting exculpatory evidence at trial. In inquiring whether the erroneous exclusion of defense evidence requires reversal, we determine whether "a reviewing court might nonetheless say that the error was harmless beyond a reasonable doubt," even if the exculpatory potential of the excluded evidence were fully realized. State v. Post, 512 N.W.2d 99, 102 (Minn. 1994) (quoting Delaware v. Van Arsdall, 475 U.S. 673, 683-84, 106 S. Ct. 1431, 1437-38 (1986)). The party claiming error has the burden of showing both the error and the resulting prejudice. State v. Loebach, 310 N.W.2d 58, 64 (Minn. 1981).

Under Minnesota law, driving at any speed in excess of 65 mph is unlawful on non-Interstate freeways and expressways. Minn. Stat. § 169.14, subd. 2 (a) (2). In areas other than those specified in section 169.14, subd. 2, any speed in excess of 55 mph is unlawful. Minn. Stat. § 169.14, subd. 2 (a) (3) (Supp. 1997). Additionally, any speed in excess of a speed limit posted by the commissioner of public safety is unlawful. Minn. Stat. § 169.14, subd. 4 (1996).

At trial, Melland contested neither Johnson's qualifications to operate the radar unit nor the accuracy of the radar's calibration. These concessions, along with Johnson's testimony that his radar unit yielded a reading of 67 mph, show that Melland's speed was greater than 65 mph. Accordingly, we conclude that the district court would have found that Melland violated the speed limit, whether it was 55 or 65 mph. See State v. Bogren, 410 N.W.2d 383, 385 (Minn. App. 1987) (radar evidence of speeding sufficient by itself to sustain conviction). See also Minn. Stat. 169.14, subd. 4 (providing the designated speed is the maximum speed, and any speed in excess of the designated speed is unlawful). Thus, any error the district court may have committed in limiting Melland's ability to prove that the applicable speed limit was 65 mph was harmless beyond a reasonable doubt. See Post, 512 N.W.2d at 102.

Finally, Melland's argument that the district court erred in denying his request for a subpoena also fails. That decision, tantamount to an evidentiary ruling, will be upheld absent an abuse of discretion. Cf. State v. Kelly, 435 N.W.2d 807, 813 (Minn. 1989) (abuse of discretion standard applies to evidentiary rulings). Minn. R. Crim. P. 22.01, subd. 3 provides that "[a] subpoena shall not be issued at the request of a defendant not represented by counsel without an order of court authorizing its issuance." Before ordering the issuance of a subpoena, a district court may require unrepresented defendants to show that a requested subpoena will be used to procure relevant evidence. In his subpoena request, Melland noted that the DOT employee's testimony was needed to establish the "accuracy of documents." But this cursory explanation did not identify the documents to be authenticated by the DOT employee or show their relevance to Melland's petty misdemeanor trial. Under these circumstances, the district court did not abuse its discretion in denying Melland's request for a subpoena.

Affirmed.