Gregory Scott Washburn, petitioner, Appellant, vs. Commissioner of Public Safety, Respondent.

may not be cited except as provided by

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

 STATE OF MINNESOTA

 IN COURT OF APPEALS

Gregory Scott Washburn, petitioner,

Appellant,

vs.

Commissioner of Public Safety,

Respondent.

 Filed August 26, 1997

 Affirmed

 Norton, Judge

Hennepin County District Court

File No. 474-168

Robert M. Christensen, Gerald Miller & Associates, P.A., 133 First Avenue North, Suite 100, Minneapolis, MN 55401-1414 (for Appellant)

Hubert H. Humphrey III, Attorney General, Jeffrey F. Lebowski, Assistant Attorney General, 525 Park Street, Suite 200, St. Paul, MN 55103 (for Respondent)

Considered and decided by Amundson, Presiding Judge, Norton, Judge, and Peterson, Judge.

 U N P U B L I S H E D O P I N I O N

 NORTON, Judge

Appellant contends the district court erred by concluding that the police had not prevented or denied his right to obtain an additional chemical test within the meaning of Minn. Stat. § 169.123, subd. 3 (1996). The police did not prevent or deny appellant's right to an additional test because they provided him a telephone and a reasonable opportunity to use it. We affirm.

 FACTS

At approximately 1:00 a.m. on September 14, 1996, Officer Charles Gollop arrested appellant Gregory Scott Washburn for driving while intoxicated. After Officer Gollop read appellant the implied consent advisory, appellant requested the right to contact an attorney. After speaking with his attorney, appellant agreed to take the Intoxilyzer test. The test revealed that appellant had an alcohol concentration of .21. Appellant then asked for an additional test. Officer Gollop explained that the police station did not provide an additional test, but appellant could arrange for an additional test on his own. Officer Gollop gave appellant a telephone. Testimony regarding appellant's vindication of his right to an additional test diverges at this point.

Officer Gollop testified that he was present the entire time appellant was using the phone. When Officer Gollop eventually asked appellant if he was done using the phone, he stated that he was done. Officer Gollop then placed appellant in a holding cell. In contrast, appellant testified that Officer Gollop was not present in the room when he was making phone calls to arrange for an additional test. According to appellant, he made three calls before finally reaching someone to administer the additional test. As soon as he began the successful call, an officer came over to him, hung up the phone, and said, "That's enough." Notably, appellant could not remember the name of the officer who allegedly hung up the phone. Appellant never obtained an additional test.

Because appellant's alcohol concentration was above .10, his driver's license was revoked pursuant to Minn. Stat. §§ 169.01, subd. 61 (1996) and 169.123, subd. 4(e) (1996). Appellant filed a petition for judicial review. Following the hearing regarding the vindication of appellant's right to additional testing, the district court sustained the revocation of appellant's driver's license. The court found that the police made a telephone available to appellant and allowed him a reasonable opportunity to make calls. Thus, the court concluded that there was no improper interference with appellant's right to an additional test.

 D E C I S I O N

Appellant claims that the district court erred by concluding that the police had not prevented or denied his right to obtain an additional test. Generally, a district court's findings of fact must be sustained unless they are clearly erroneous. Frost v. Commissioner of Pub. Safety, 348 N.W.2d 803, 804 (Minn. App. 1984). Conclusions of law, such as whether police have prevented or denied an additional test, may be overturned only upon a showing that the district court erroneously applied the law to the facts. Berge v. Commissioner of Pub. Safety, 374 N.W.2d 730, 732 (Minn. 1985).

A person who is tested under the implied consent law has the right to have someone of the person's own choosing administer an additional chemical test. Minn. Stat. § 169.123, subd. 3(a) (1996). Nonetheless, the failure or inability to obtain an additional test does not preclude the admission of Intoxilyzer test results "unless the additional test was prevented or denied by the peace officer." Id. at subd. 3(b).

In determining whether police have prevented or denied an additional test, the court distinguishes between an officer's failure to assist a motorist in obtaining the test and an officer's hampering a motorist's attempt to obtain the test. Theel v. Commissioner of Pub. Safety, 447 N.W.2d 472, 474 (Minn. App. 1989), review denied (Minn. Jan. 8, 1990). Generally, "[t]he only obligation an officer has in assisting the defendant in obtaining an additional test is to allow defendant use of a phone." Frost, 348 N.W.2d at 804; see also State v. Hatlestad, 347 N.W.2d 843, 845 (Minn. App. 1984) (officer has no duty to furnish supplies or facilitate transportation for an additional test). On the other hand, if an officer hampers the motorist's attempt to secure an additional test, then results of the Intoxilyzer test are inadmissible. See State v. Shifflet, 556 N.W.2d 224, 225, 228 (Minn. App. 1996) (chemical test results were inadmissible where officer's refusal to allow independent test administrator access to motorist prevented motorist from exercising his right to additional test); Theel, 447 N.W.2d at 474 (holding that defendant's statutory right to obtain additional test was prevented or denied by police who said, "Forget it, they are all sleeping," after defendant had called four hospitals that refused to send personnel to jail to perform test and was in the process of calling attorney to assist him).

Appellant argues that the officer's conduct in this case was equivalent to the officer's conduct in Theel, 447 N.W.2d at 474. As the commissioner concedes, if the officer did hang up the receiver and say, "That's enough," it would appear that appellant's right to an additional test was prevented by police. In contrast to appellant's testimony, however, Officer Gollop testified that he asked appellant if he was finished with the phone and appellant stated he was. Thus, Officer Gollop believed appellant's right to an additional test was vindicated.

In concluding that appellant's right to an additional test was not prevented or denied by police, the district court made no finding regarding the credibility of the testimony of Officer Gollop and appellant. The commissioner argues that, in light of the district court's conclusion that police did not prevent or deny appellant from securing an additional test, the district court implicitly found Officer Gollop's testimony regarding the circumstances more credible. See Umphlett v. Commissioner of Pub. Safety, 533 N.W.2d 636, 639 (Minn. App. 1995) (deferring to trial court's implicit finding of officer's credibility, based on trial court's resolution of legal issue that depended on that testimony), review denied (Minn. Aug. 30, 1995). In Umphlett, the defendant claimed that his right to additional testing was violated because he requested an additional test and was not allowed to use the telephone. Id. at 638. The arresting officer testified that the defendant never requested an additional test. Id. In sustaining the revocation of defendant's driver's license, the district court made no finding regarding whether the defendant requested an additional test. Id. On appeal, this court held that, although the district court did not make a specific finding on the credibility of the witnesses, by sustaining the revocation of the defendant's driver's license, the court "implicitly found that the officer's testimony was more credible regarding the request for a second test." Id. at 639. Therefore, this court concluded that the defendant was not denied his right to an additional test. Id.

The testimonies of Officer Gollop and appellant differed regarding whether appellant's right to an additional test was vindicated. Nonetheless, as in Umphlett, we conclude that the district court believed Officer Gollop's testimony, due to its conclusion that appellant's right to additional testing was vindicated. Moreover, because it is the district court's role to assess the credibility of witnesses and to weigh conflicting testimony, this court must defer to the district court's determination. Frost, 348 N.W.2d at 804. Therefore, we affirm the district court's order sustaining the revocation of appellant's driver's license.

  Affirmed.