*287OPINION
COATS, Chief Judge.Rodney A. McCarthy appeals his convietion for driving under the influence.1
McCarthy argues that the trial court should have suppressed his Datamaster breath test result, and all statements he made during the DUI processing, because the officer who administered the breath test did not make an audio recording of the DUI processing. We uphold the trial court's ruling because MeCarthy waived this issue through inadequate briefing, because the trial court found that MeCarthy was not subjected to interrogation during the DUI processing, and because the trial court found that the officer's failure to record the processing was inadvertent.
McCarthy next argues that it was error for the trial court to allow the State to introduce the reports that verified the calibration of the Datamaster in the absence of live testimony from the authors of these reports; McCarthy contends that the admission of the reports violated his right of confrontation under the United States Constitution. We adhere to our prior decisions (and to the decisions of almost every other jurisdiction to have considered this issue) holding that calibration reports for breath test machines are business records, and that the introduction of these records does not implicate the confrontation clause.
McCarthy further argues that the trial court erred when it refused to instruct the jury that one element of the offense of driving under the influence is that the defendant must be criminally negligent with respect to whether he was too impaired to drive. We conclude that McCarthy's argument in favor of this proposed instruction is based on a mistaken interpretation of our decision in Valentine v. State, 155 P.3d 331 (Alaska App.2007).2
McCarthy contends that the trial court erred when it refused to let him introduce prior calibration reports for the Datamaster machine that was used to test his breath. According to these reports, this Datamaster machine often reported an alcohol content that was slightly higher-between .004 and .008 percent higher-than the target value of the sample being tested, but still within the acceptable margin of error set by law. We uphold the trial court's ruling, both because this variation is within the acceptable margin of error, and also because this amount of variation could not possibly have made a difference in McCarthy's case-since his blood aleohol reading was .214 percent.
Finally, McCarthy argues that the trial court erred in excluding a document showing that, several months after McCarthy's breath test, the Datamaster machine developed a problem: the machine no longer accepted air from its intake tube, leading to breath test readings of 0.00 percent in cases where the person being tested was clearly intoxicated. We uphold the trial court's decision to exclude this evidence-because the evidence of this later Datamaster malfunction had essentially no relevance to the accuracy of McCarthy's breath test.
Underlying facts and trial court proceedings
On July 10, 2009, Trooper Jack LeBlane stopped McCarthy's vehicle because McCarthy was weaving in and out of his lane. After investigation, Trooper LeBlane arrested McCarthy for driving under the influence, and then he transported McCarthy to the station for a breath test. Although the trooper recorded his initial contact with McCarthy, he inadvertently, or through an equipment malfunction, failed to make an audio recording of the DUI processing at the station.
After a fifteen-minute observation period and several attempts, McCarthy eventually provided a breath sample. This sample yielded a test result of .214 percent blood aleohol. MeCarthy was charged with driving under the influence.
Before trial, McCarthy moved to suppress his breath test result and all statements he made during the breath testing process be*288cause of the trooper's failure to record the processing. MceCarthy also requested a Thorne jury instruction-4e., an instruction telling the jury to presume that a recording of the processing would have been favorable to him.3 After an evidentiary hearing on his motion to suppress, District Court Judge Kevin Miller denied MeCarthy's motion. Judge Miller found that the trooper's failure to record was inadvertent. The judge also concluded that the trooper was not required to record the DUI processing because no custodial interrogation occurred, and no incriminating statements were made, during the processing. Judge Miller therefore admitted the breath test result, and he denied McCarthy's request for a Thorne instruction.
On a separate issue, McCarthy objected to the admission of the two reports verifying the calibration of the Datamaster on dates before and after his breath test. He argued that admission of these reports without testimony from the authors violated his right to confrontation, and that the reports lacked proper evidentiary foundation without the live testimony of the authors. Judge Miller rejected these arguments and admitted both documents.
McCarthy moved to admit the Datamaster calibration reports from the fifteen months prior to his breath sample, to show that the Datamaster was repeatedly yielding test results that were slightly higher (between .004 and .008 percent higher) than the actual chemical content of the samples being tested. Judge Miller declined to let McCarthy introduce this evidence. The judge ruled that as long as the testing variations were within the working tolerance of the Datamaster, the evidence was irrelevant.
McCarthy also asked to introduce evidence showing that this Datamaster began malfunctioning some four months after McCarthy's breath test. Again, Judge Miller concluded that this proposed evidence was irrelevant.
McCarthy asked Judge Miller to instruct the jury that, in prosecutions for driving under the influence, the State was required to prove that the defendant was criminally negligent with respect to whether he was too impaired to safely operate a motor vehicle. Judge Miller declined to give this jury instruction.
The trooper's failure to record the DUI processing does not merit suppression of the Datamaster test result
McCarthy's first claim is that the trial court erred in admitting the Datamaster test result in the absence of an audio or video recording of the DUI processing at the police station. While McCarthy recounts the trial court's findings relating to his suppression motion (in particular, the finding that the trooper's failure to record the DUI processing was inadvertent), he does not present any argument regarding Judge Miller's rulings, he does not articulate which of the judge's findings or rulings he believes to be erroneous, and he does not cite any legal authority. Accordingly, we find that McCarthy has waived this issue by failing to adequately brief it.4
Moreover,; even if McCarthy had not waived this issue, we would affirm the trial court's ruling. Judge Miller found that the trooper did not question McCarthy during the DUI observation period and that McCarthy did not make any incriminating statements during this time. Judge Miller also concluded that the trooper's failure to record was inadvertent. Furthermore, the judge found there was no evidence of any behavior during the processing and testing to suggest that alcohol in McCarthy's mouth affected the Datamaster test result. Because there was no custodial interrogation, because the officer's failure to record was inadvertent, and because there was no evidence of any reason to doubt the test result, no basis exists to suppress the Datamaster result.5
*289With regard to McCarthy's request for a Thorne instruction,6 the trooper's failure to record the DUI processing constitutes a failure to collect evidence, not a destruction of evidence. The general rule is that the State has no duty to collect physical evidence, and that the State's duty to preserve evidence applies only to physical evidence that has actually been gathered.7 Because McCarthy did not allege (much less show) that the trooper destroyed any evidence, McCarthy was not entitled to a presumption that a recording would have been favorable to him.
Admission of the verification of calibre, tion without testimony did not violate McCarthy's right of confrontation
At trial, McCarthy objected to the admission of the two reports that verified the calibration of his Datamaster machine on June 13, 2009 and on August 14, 2009 (.e, both before and after his July 10th breath test). McCarthy argued that the admission of these reports, without testimony from the people who ran the calibration tests and wrote the reports, violated his right of confrontation. Judge Miller overruled MeCar-thy's objection to the admission of the reports.
On appeal, McCarthy argues that admission of the calibration reports without testimony from the reports' authors violated his right of confrontation under the Sixth Amendment as construed in Melendez-Diaz v. Massachusetts.8
McCarthy acknowledges that, both before and after Melendez-Diaz, this Court has held that Datamaster calibration reports are non-testimonial business records, and that therefore the admission of these reports does not implicate the confrontation clause. See Abyo v. State, 166 P.3d 55, 58-60 (Alaska App.2007), and Hamilton v. State, unpublished, Alaska App. Memorandum Opinion No. 5650, 2010 WL 4260608, *3 (October 27, 2010). But MeCarthy asks us to overrule Abyo.
McCarthy argues that Datamaster calibration reports are prepared in anticipation of criminal litigation, albeit not for any specific case. We rejected this argument in Abyo: we concluded (in line with the majority of courts) that reports verifying the calibration of breath testing machines are not "testimonial" evidence for purposes of the confrontation clause, and that these reports may be admitted without the testimony of the individuals who prepared them. Abyo, 166 P.3d at 59-60.
Several courts have considered this same issue since the United States Supreme Court issued its decision in Melendez-Diaz, and these courts have almost uniformly agreed that breath machine calibration records are non-testimonial.9 We therefore adhere to our prior decisions on this issue.
McCarthy argues he should have been able to cross-examine the authors of the calibration reports because there was a question as to the accuracy of this particular Datamaster. But this argument does not pertain to the confrontation issue under Melendez-Diaz, or to whether the calibration report is "testimonial" for Sixth Amendment purposes. Instead, it is a due process argument regarding McCarthy's right to challenge the accuracy of the Datamaster result. Under Alaska law, the Datamaster result is presumptively admissible if the calibration of the Datamaster *290machine has been verified every sixty days.10 Onee the State offered calibration documents to prove this foundational requirement, the trial court properly admitted McCarthy's Da-tamaster result.
McCarthy was free to present admissible evidence impeaching the accuracy of the breath test.11 He could have called the authors of the calibration reports, or any other witness, to explore the issue of the Datamas-ter's accuracy. But that evidence would go to the weight of the breath test result, not its admissibility.12
The State was not required to prove that McCarthy was criminally negligent with respect to whether he was too impaired to drive
McCarthy asked Judge Miller to instruct the jury that the State was required to prove, as an element of driving under the influence, that McCarthy was at least negligent with respect to whether he was too impaired to drive. Judge Miller denied McCarthy's request.
This Court has repeatedly held that, in prosecutions for driving under the influence, the government need not prove that the defendant acted with any culpable mental state with respect to the cireumstance that made the defendant's driving illegal-either the fact that the defendant was impaired by intoxicants, or the fact that the defendant's blood-alcohol level exceeded the legal limit.13 Judge Miller relied on this line of cases when he ruled that the State was not required to prove that McCarthy was aware of his impairment, or even that MeCarthy should have been aware of his impairment (e., that McCarthy acted negligently with respect to this cireumstance).
McCarthy argues, however, that this Court departed from this line of authority when we issued our decision in Valentine v. State, 155 P.3d 331 (Alaska App.2007).14
The defendant in Valentine argued that, despite our prior decisions on this point, it was unconstitutional to allow the government to convict motorists of driving under the influence unless the government proved that the motorists were at least negligent with respect to the fact that they were impaired, or that their blood alcohol level exceeded the legal limit. In support of this argument, the defendant in Valentine relied on the Alaska Supreme Court's decision in State v. Hazelwood, 946 P.2d 875 (Alaska 1997).
The Hazelwood decision holds that when conduct is criminal only under a particular cireumstance, the due process clause requires the government to prove that the defendant was at least negligent with respect to that cireumstance. Hazelwood, 946 P.2d at 879. Relying on Hazelwood, the defendant in Valentine argued that the offense of driving under the influence was governed by the same rule: driving is legal unless the motorist is under the influence, and therefore the *291government should be required to prove that the motorist was at least negligent with respect to the circumstance that they were under the influence. See Valentine, 155 P.3d at 343.
This Court rejected the defendant's argument because we concluded that when the government proves that a motorist (1) knowingly consumed intoxicants and (2) knowingly operated or took control of a motor vehicle, this of itself establishes that the motorist was at least negligent with respect to the cireum-stance that they were under the influence. . Valentine, 155 P.3d at 342-43. Here is the pertinent portion of our opinion in Valentine:
To convict a defendant of driving while under the influence, the State is not required to prove any mens rea with respect to the cireumstance of having consumed too much aleohol to legally drive. But the State must prove that the defendant was legally intoxicated (either because his blood alcohol level met or exceeded the statutory limit within four hours of driving, or because he was under the influence at the time of driving) and [must prove that the defendant] knowingly drank and drove; it is implicit in the proof of these elements that the defendant was eriminally negligent as to the cireumstance of being too impaired to legally drive. The conduct of consuming aleohol puts a person on notice that he may be [or become] impaired.
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[Proof that the defendant was legally intoxicated and that the defendant knowingly consumed alcohol and drove is sufficient to establish that the defendant was negligent with respect to the cireumstance that he was too impaired to legally drive.
Valentine, 155 P.3d at 342 & 343 (citation omitted).
In MeCarthy's brief to this Court, he focuses on one portion of this passage from Valentine: the portion where we declared that, when the government proves that the defendant was intoxicated, and that the defendant knowingly drank alcoholic beverages and knowingly drove a vehicle, "it is implicit ... that the defendant was criminally negligent as to the cireumstance of being too impaired to legally drive."
McCarthy interprets this language to mean that the offense of driving under the influence implicitly requires proof of an additional element: that the defendant acted negligently with respect to the cireumstance that they were impaired. But this is a misreading of Valentine.
In Valentine, we explicitly re-affirmed our line of cases holding that the government is mot required to prove that the defendant acted with any culpable mental state with respect to the fact that they were impaired, or that their blood aleohol level was above the legal limit. Id. at 342-43. The above-quoted passage from Valentine was not meant to disavow this line of cases. Rather, the passage explains why this line of cases is consistent with the requirements of the due process clause, as interpreted in Hazelwood.
Hazelwood holds that when an activity is illegal only under a particular cireumstance, the due process clause requires the government to prove (as a minimum predicate for imposing criminal liability) that the defendant acted at least negligently with respect to that cireumstance. Valentine holds that, in prosecutions for driving under the influence, this due process requirement is implicitly satisfied by proof that the defendant knowingly drank alcoholic beverages and either became impaired or drank to the point where their blood aleohol level exceeded the legal limit.
McCarthy suggests that if Valentine is interpreted in this manner, it leads to results that violate the rule against irrebuttable or conclusive presumptions in criminal cases.15 McCarthy interprets Valentine to say (1) that the offense of driving under the influence requires proof of an additional element (proof that the defendant acted negligently with respect to the fact of their impairment), and (2) that a finder of fact can presume, based on proof that the defendant knowingly drank alcoholic beverages and became impaired, that this additional element has been proved.
*292But, again, this argument is based on a misreading of Valentine. As we just explained, the Valentine decision rejects the notion that there is an extra "negligence" element to be proved in a DUI prosecution. Rather, Valentine reiterates that the government need not prove any culpable mental state with respect to the cireumstance that the defendant was impaired, or that the defendant's blood alcohol level exceeded the legal limit. Valentine explains that this is sufficient to satisfy the demands of due process because, as a matter of law, proof that the defendant knowingly drank aleoholic beverages, coupled with proof that the defendant became impaired, or that the defendant drank to the point where their blood alcohol level exceeded the legal limit, is itself sufficient to meet the minimal due process requirement for imposing eriminal liability.
For these reasons, we uphold Judge Miller's rejection of McCarthy's proposed jury instruction.
The trial court did not abuse its discretion in refusing to admit the Datamaster calibration reports from the prior fifteen months
At trial, McCarthy moved to admit the calibration reports for his Datamaster from the fifteen months preceding his breath test. These calibration reports showed that the Datamaster repeatedly yielded test results that were slightly higher than the target value of the samples being tested (between .004 and .008 percent higher), but still within the working tolerance of the instrument.
McCarthy argued that this evidence was admissible to show that the Datamaster used for his breath test was unreliable and not properly calibrated, and he argued that he had a due process right to introduce this evidence.
Judge Miller ruled that these calibration reports were irrelevant-because the testing variations shown in these reports were all within the acceptable working tolerance of the Datamaster, and because, under AS 28.90.020, it is irrelevant whether a Datamas-ter machine has testing variations within this working tolerance.16
Judge Miller told MeCarthy that, notwithstanding the statute, he would allow MeCar-thy to introduce the calibration reports to attack the accuracy of the Datamaster if McCarthy had an expert witness who could explain how testing variations within the working tolerance of the instrument were somehow relevant to demonstrating the possibility that this Datamaster machine might be susceptible to testing variations that were outside the working tolerance of the machine. MeCarthy did not present such an expert.
On appeal, McCarthy argues that Judge Miller abused his discretion when he denied MeCarthy's motion to introduce the calibration reports from the fifteen months prior to his breath test. This issue is inadequately briefed. McCarthy does not explain why Judge Miller's ruling was wrong, and he does not cite any law to support his argument.
But even if McCarthy had adequately briefed this issue, we would affirm Judge Miller's ruling. Under AS 28.90.020, a breath test result from a properly calibrated instrument is not affected by the instrument's testing variations, as long as those variations are within the machine's working tolerance. In other words, the fact that the breath test result may be higher or lower than the actual alcohol content of the suspect's blood is irrelevant so long as the machine is functioning within the legally pre-seribed working tolerance.
As we explained, Judge Miller told McCarthy that he could use this evidence to challenge the validity or accuracy of the breath test result if McCarthy presented an expert witness who could explain how variations in the Datamaster calibration results might indicate that, in actual use, the machine would *293yield test results outside the bounds of its working tolerance. But McCarthy did not do so.
Moreover, McCarthy does not explain what prejudice he suffered from the exclusion of this evidence. The Datamaster's calibration tests yielded only slight variations from the norm: test results that were between .004-.008 percent higher than the target values of the samples being tested. McCarthy's test result was .214 percent. Even if McCarthy's Datamaster was consistently high by as much as .008 percent, McCarthy's blood aleohol content would still have been significantly over the legal limit {.08 percent).
Because this issue is inadequately briefed, McCarthy did not produce any evidence suggesting that the prior calibration reports were relevant, and because the potential inaccuracy of the Datamaster was harmless beyond a reasonable doubt, we reject McCarthy's claim.
The trial court did not err in excluding evidence of a Datamaster malfunction that occurred months after McCarthy's breath test
McCarthy argues Judge Miller erred by not allowing him to question a police officer about a malfunction that arose in this same Datamaster machine some four months after McCarthy's breath test. McCarthy argues that this evidence was relevant because it cast doubt on his breath test.
Ketchikan Police Officer Derek McGarri-gan testified that the Datamaster used to test McCarthy's breath on July 10, 2009 began to malfunction on approximately November 21, 2009. Officer McGarrigan testified that an October 2009 test of the Datamas-ter's calibration indicated that the Datamas-ter was functioning properly at that time. But on November 21st, the machine was used to test the breath of an arrestee who was obviously intoxicated, and the test result was 0.00 percent.
After the machine malfunctioned in a similar manner a couple of days later, it was taken out of service. (In between the two malfunctions, the Datamaster functioned correctly.) Inspection of the machine revealed that the valve which allowed the breath sample to enter the testing chamber was not working; the valve was not allowing the breath sample to enter the chamber to be tested.
McCarthy asserts that the jury could have concluded the Datamaster was malfunctioning in July if it malfunctioned in November. But Judge Miller reasonably rejected this proposition. There was no evidence of any malfunction in the Datamaster before November 21, 2009, and McCarthy provided no evidence that the November malfunction could potentially have affected his July breath test result.
Furthermore, the type of malfunction that occurred here-a valve failure-prevented an arrestee's breath sample from reaching the testing chamber, thus leading to a false reading of 0.00 percent (%.e., absolutely no alcohol), even when the suspect was clearly intoxicated. McCarthy's Datamaster breath test result was .214 percent. Because the alcohol in McCarthy's breath triggered this reading in the Datamaster, it is obvious that the valve was working at the time. In other words, the malfunction that occurred in November-a complete blockage of intake air-could not have occurred during McCarthy's breath test.
For these reasons, we conclude that Judge Miller properly excluded the evidence of the November malfunction.
Conclusion
The judgment of the district court is AFFIRMED.
. AS 28.35.030(a)(2).
. Reversed on other grounds, 215 P.3d 319 (Alaska 2009).
. See Thorne v. Department of Public Safety, 774 P.2d 1326, 1331-32 (Alaska 1989).
. See, e.g., Kingery v. Barrett, 249 P.3d 275, 285 (Alaska 2011); Martinson v. Arco Alaska, Inc., 989 P.2d 733, 737-38 (Alaska 1999); City of Fairbanks v. Rice, 20 P.3d 1097, 1106 (Alaska 2000); Vickers v. State, 175 P.3d 1280, 1287 (Alaska App.2008); Buckwalter v. State, 23 P.3d 81, 88 (Alaska App.2001).
. See Stephan v. State, 711 P.2d 1156, 1162-63 (Alaska 1985).
. See Thorne v. Department of Public Safety, 774 P.2d 1326, 1331-32 (Alaska 1989).
. Snyder v. State, 879 P.2d 1025, 1028 (Alaska App.1994), reversed on other grounds, 930 P.2d 1274 (Alaska 1996); March v. State, 859 P.2d 714, 716 (Alaska App.1993).
. 557 U.S. 305, 129 S.Ct. 2527, 174 L.Ed.2d 314 (2009).
. See, e.g., State v. Kramer, 153 Idaho 29, 278 P.3d 431, 434-38 (App.2012) (distinguishing for confrontation clause purposes between evidence offered as direct proof of an element and evidence that bears only on the admissibility or credibility of other evidence, like verification of calibration reports, inspection reports, and maintenance records); Commonwealth v. Zeininger, 459 Mass. 775, 947 N.E.2d 1060, 1069-1070 (2011) (same); Matthies v. State, 85 So.3d 838, 843-44 (Miss.2012) (citing cases addressing this issue post-Melendez-Diaz ); see also State v. Britt, 283 Neb. 600, 813 N.W.2d 434, 439 (2012) (holding that the certification of the alcohol solution used to test the calibration of the breath test instrument is not testimonial).
. AS 28.35.033(d); 13 AAC 63.100.
. Gilbreath v. Anchorage, 773 P.2d 218, 222 (Alaska App.1989); see Williams v. State, 884 P.2d 167, 174 (Alaska App.1994), abrogated on other grounds in State v. Coon, 974 P.2d 386 (Alaska 1999).
. Gilbreath, 773 P.2d at 222; Williams, 884 P.2d at 174.
. See Morgan v. Anchorage, 643 P.2d 691, 692 (Alaska App.1982) (rejecting the claim that the government must prove that the motorist was aware that they were under the influence); Van Brunt v. State, 646 P.2d 872, 873 (Alaska App.1982) (holding that a conviction for driving under the influence does not require proof that the motorist knew they were under the influence, or that their blood or breath alcohol level exceeded the legal limit; the fact that the motorist knowingly drank and drove was enough to support a conviction); Cooley v. Anchorage, 649 P.2d 251, 253 n. 3 (Alaska App.1982) (rejecting the claim that the Anchorage ordinance defining the offense of driving under the influence violated the due process clause because it required no criminal intent, and because motorists had no way of knowing whether their blood or breath alcohol had reached a level that placed them in violation of the ordinance); Hoople v. State, 985 P.2d 1004, 1006 (Alaska App.1999) (stating that the offense of driving under the influence "does not require proof of any culpable mental state regarding ... the fact that the driver was intoxicated or that the driver's blood-alcohol content exceeded [the legal limit]"); State v. Simpson, 53 P.3d 165, 167 (Alaska App.2002) (noting that this Court had [previously] rejected the notion that a[ DUI] defendant must know that they are under the influence").
. Reversed on other grounds, 215 P.3d 319 (Alaska 2009).
. See Sandstrom v. Montana, 442 U.S. 510, 99 S.Ct. 2450, 61 L.Ed.2d 39 (1979).
. AS 28.90.020 reads: "Breath test result validity. Except for an offense under AS 28.35.280, if an offense described under this title requires that a chemical test of a person's breath produce a particular result, and the chemical test is administered by a properly calibrated instrument approved by the Department of Public Safety, the result described by statute is not affected by the instrument's working tolerance."