¶ 1. Defendant appeals the denial of his motion to suppress evidence that ultimately led to defendant’s DUI processing. On February 24, 2006, a state trooper stopped to render roadside assistance to defendant, who was some fifty miles off course. After smelling alcohol and having difficulty understanding defendant when he spoke, the trooper administered a preliminary breath test (PBT) and conducted field-sobriety exercises in order to determine whether defendant was driving under the influence in violation of 23 V.S.A. § 1201(a). Defendant seeks to suppress the PBT and all the evidence obtained thereafter, arguing that his participation was not voluntary. Defendant also argues that his admissions regarding alcohol consumption should be suppressed. We affirm.
¶ 2. Defendant’s car was stopped in the breakdown lane of 1-91 with its four-way hazard lights flashing when a state trooper approached to render assistance at approximately 10:30 p.m. Defendant indicated to the trooper that he had run out of gas while on his way to Mount Snow and had just called 911. The trooper found this explanation to be odd, given that defendant had passed the exit to Mount Snow approximately fifty-five miles earlier. While defendant was speaking, the trooper smelled an odor of intoxicants.
¶ 3. After checking defendant’s license, the trooper discussed contacting the American Automobile Association (AAA) for help. He explained that he had internet access in his cruiser and asked defendant if he would “mind sitting in there” while the trooper checked on whether roadside assistance was available. Defendant agreed and, after the trooper frisked him for weapons, walked around to the passenger side of the cruiser and got inside. While inside the cruiser searching the internet, the trooper spoke "with defendant about his work and about the route he had taken to Vermont. The trooper smelled “a strong odor of alcohol” coming from defendant’s person and noticed that defendant’s eyes were *445 bloodshot and watery. The trooper had trouble understanding defendant at times, because his speech was not “smooth and clear.” The trooper asked defendant whether he had consumed any alcohol, and defendant replied, “[n]ot much.” On further questioning, defendant admitted that “he had [had] a sip of his mother’s pina colada approximately four hours earlier.”
¶ 4. The trooper told defendant the best thing he could do was “to be honest” and told him to blow into a PBT device. Defendant did so. The trooper then explained to him that the result was almost twice the legal limit in Vermont and again asked defendant how much he had had to drink. Defendant admitted he had consumed “three or four beers.” The trooper then told defendant that he was going to administer field-sobriety tests. After defendant showed signs of impairment on the first test, the trooper asked him to step out of the cruiser and administered several other field-sobriety exercises. When defendant showed further signs of intoxication, he was placed under arrest for DUI and taken to the barracks, where a breathalyzer test confirmed he had a blood-alcohol content (BAC) of .141.
¶ 5. Defendant moved to suppress the statements that he made to the trooper after entering the cruiser, as well as the PBT and all the evidence obtained thereafter. Defendant claimed his participation in these tests was compelled. The trial court denied his motion.
¶ 6. Defendant raises five issues on appeal, claiming that: (1) field-sobriety exercises and PBTs are searches under the Fourth Amendment of the United States Constitution and Article 11 of the Vermont Constitution; (2) Vermont drivers have a right to refuse PBTs and field-sobriety tests; (3) his participation in the PBT and field-sobriety tests was involuntary; (4) the statements he made to the trooper after being informed of his PBT results should be suppressed because the trooper failed to read him his
Miranda
warnings, in violation of the Fifth Amendment of the United States Constitution and Article 10 of the Vermont Constitution; and (5) the trial court erred in finding that probable cause to arrest existed before the PBT was administered. When reviewing a motion to suppress, we uphold the trial court’s findings unless clearly erroneous, while reviewing the court’s legal conclusions de novo.
State v. Lawrence,
*446 I.
¶ 7. We first address defendant’s claim that field-sobriety exercises and PBTs are “searches” under the Fourth Amendment of the United States Constitution and Article 11 of the Vermont Constitution. We have held that the administration of field-sobriety tests is a seizure for the purposes of the Fourth Amendment.
State v. Gray,
¶ 8. Whether we classify field-sobriety exercises as a “search” or a “seizure,” their administration is the kind of investigatory detention the United States Supreme Court contemplated in
Terry v. Ohio,
¶ 9. We have not yet addressed whether the administration of a PBT is a search or seizure pursuant to either the Fourth Amendment or Article 11. “A [Fourth Amendment] ‘search’ occurs when an expectation of privacy that society is prepared to
*447
consider reasonable is infringed.”
United States v. Jacobsen,
¶ 10. The United States Supreme Court has held that “a compelled intrusion into the body for blood to be analyzed for alcohol content” constitutes a search under the Fourth Amendment.
Skinner,
¶ 11. The administration of a PBT raises similar concerns. Like breathalyzer tests, PBTs provide a chemical analysis of a citizen’s breath for the purposes of calculating blood-alcohol content. The PBT requires the production of “deep lung” breath and tests it for alcohol content. These processes appear to be no less private than those involved in a breathalyzer or a blood test. The administration of the test — in which one must breathe into a small, chemical-analysis device — is a physical intrusion. Com
*448
mon recognition of the sanctity of the person leads us to conclude that a PBT “intrudes into [an] area[]” that is the “subject of legitimate expectations of privacy,” and thus is a search under both the Vermont and United States Constitutions.
Bryant,
¶ 12. Having concluded that the administration of a PBT constitutes a search, we must decide when it is “reasonable” for law-enforcement officers to use this investigatory method to collect evidence. In order to determine whether this search is “reasonable” under the Fourth Amendment, we “balanc[e] the need to search . . . against the invasion which the search . . . entails.”
Terry,
¶ 13. “Under both the Vermont and the United States Constitutions, we have recognized that [a] brief detention, its scope reasonably related to the justification for the stop and inquiry, is permitted in order to investigate the circumstances that provoke suspicion.”
State v. Ford,
¶ 14. PBTs are common tools in the investigatory kit officers use to ascertain whether probable cause exists to believe that an individual has been driving under the influence of alcohol. PBTs are “quick and minimally intrusive” yet “perform[] a valuable function as a screening device” to detect drunk driving.
State v. Orvis,
¶ 15. The trial court concluded that the trooper had “reasonable grounds to request [that defendant submit to a [PBT] . . . [and that] [t]he results of that preliminary test provided a further basis to request performance of other field sobriety exercises.” These findings are not challenged on appeal. 2 The officer’s administration of these tests thus met the constitutional requirements imposed by Article 11 and the Fourth Amendment, and we affirm the denial of the suppression motion on these grounds.
II.
¶ 16. Defendant next argues that Vermont drivers have a right to refuse to participate in PBTs and field-sobriety exercises when *450 suspected of DUI. Defendant claims that his participation in these investigative procedures was not voluntary. Accordingly, defendant maintains, that, though he did not refuse to perform these tests, this evidence must be suppressed.
¶ 17. Defendant is correct that he may refuse to submit to these tests. The trooper may not physically force him to perform the field-sobriety exercises or to blow into the PBT device.
State v. Blouin,
¶ 18. Defendant’s failure to challenge the trial court’s findings — which clearly support the conclusion that he was not forced to take the PBT nor participate in the field-sobriety exercises — renders his legal argument without force. We dismissed a similar argument in
State v. Badger,
¶ 19. Here, the trial court found that “the trooper had reasonable grounds to request that [defendant submit to a PBT” and that “[t]he trooper did not order [defendant] to perform [the PBT or field-sobriety] tests.” (emphasis added). These findings, which are supported by the trooper’s testimony at the suppression hearing, directly contradict defendant’s claim that his submission to the PBT and field-sobriety tests was less than voluntary. Without a challenge to these findings — or further factual development at the hearing, such as testimony from defendant indicating that he was coerced to participate against his will — we reject defendant’s argument that circumstances amounting to no more than a classically mundane police encounter rendered his participation involuntary.
III.
¶ 20. Defendant next argues that he was “in custody” when the trooper informed him, after the administration of the PBT, that his blood-alcohol content was almost twice the legal limit. The trooper’s failure to read him his Miranda rights at this point, he argues, violated his rights under the Fifth Amendment to the United States Constitution and Article 10 of the Vermont Constitution. Specifically, he claims that the statements he made following the PBT — most notably, his indication that he had had “three or four beers” — should be suppressed. We conclude that the admission of defendant’s statements was harmless error.
¶ 21. Any error below — be it of constitutional or nonconstitutional dimension — “which does not affect substantial rights shall be disregarded.” V.R.Cr.P. 52(a); see also
State v. Oscarson,
¶22. The suppression of defendant’s statements about his alcohol consumption has no bearing on the outcome of his case, because other evidence was sufficient to support the trooper’s decision to arrest defendant for DUI. Before the PBT was administered, the trooper observed a strong odor of intoxicants *452 about defendant’s person, noted that defendant had bloodshot and watery eyes, and had trouble understanding defendant because his speech was muddled. Defendant indicated that he had missed the exit for his destination by approximately fifty-five miles. When asked if he had consumed any alcohol, defendant first responded, “not much.” On further questioning, he indicated, apparently untruthfully given the immediate and strong odor of intoxicants, that he had had a sip of his mother’s pina colada about four hours earlier.
¶ 23. At this point, the PBT was administered. The result of the PBT, by itself, provided “reasonable grounds” for defendant’s further detention for the purposes of obtaining an evidentiary test pursuant to 23 V.S.A. § 1202(a)(3). Section 1202(a)(3) requires Vermont drivers to take an evidentiary test — generally, a breathalyzer — when the officer has “reasonable grounds” to believe that person is intoxicated. See also
State v. Orvis,
IV.
¶ 24. Defendant’s last argument is that the trial court erred in finding that probable cause for the arrest existed before the PBT, regardless of the evidence garnered by the administration of the field-sobriety tests. We do not reach this question because this finding — if erroneous — was also harmless error.
¶25. The trial court concluded that defendant’s participation in the PBT and field-sobriety exercises was not compelled, and defendant does not contest those findings here. See supra, ¶¶ 18-19. Based on these findings, the trial court denied defendant’s motion to suppress the results of the PBT and field-sobriety tests. Considering defendant’s poor performance in these exercises, there is no question that the trooper had probable cause to *453 arrest after the administration of the field-sobriety tests. The trial court’s statement that probable cause also existed earlier during the encounter between trooper and defendant does not change the outcome — either way, the trooper had probable cause to make the arrest when he did.
Affirmed.
Notes
Our standard is reflected in 23 V.S.A. § 1203(f), in which the Legislature specifically stated that a law-enforcement officer may request that a driver take a PBT when the officer has “reason to believe” that the driver has been operating his vehicle while under the influence.
In fact, at oral argument, defendant conceded that the trooper had reasonable suspicion that defendant was driving under the influence before the trooper administered the PBT and field-sobriety exercises.
