Hector Guzman (Defendant) appeals his conviction of possession of marijuana with intent to distribute. He pled guilty to the charge, reserving the right to appeal the district court’s denial of his motion to suppress evidence. On appeal, Defendant argues that his constitutional rights were violated during his detention at the border patrol checkpoint where the marijuana was found. We determine the district court could find the border patrol agent had reasonable suspicion to prolong Defendant’s detention and, therefore, affirm the denial of his motion to suppress.
Defendant was stopped at a fixed border patrol checkpoint on 1-10 west of Las Cruces. As Agent Douglas Robinson approached Defendant’s vehicle, he noticed from five or six feet away a strong odor of air freshener emanating from the vehicle. Two air fresheners hung from the rear view mirror. Based on Robinson’s more than three years’ experience as a border patrol agent, he knew deodorizers were often used to mask the odor of unlawful drugs. When Robinson asked Defendant about his citizenship, Defendant handed over an 1-551 permanent resident alien card. Robinson examined the document to determine if it appeared genuine and satisfied himself that Defendant was lawfully within this country. He then asked where Defendant was coming from and whether Defendant was the owner of the vehicle. In response to the second question, Defendant said that he was the owner and asked if Robinson would like proof. When Defendant handed over the truck registration materials, Robinson observed that Defendant’s hands were shaking and his eyes were darting around, avoiding making eye contact with Robinson. Noting that traffic was beginning to back up, Robinson then referred Defendant to a secondary area while Robinson went to the checkpoint inspection trailer to compare the registration with the immigration document. Agent John Howarth, a second border patrol agent, approached the truck at the secondary area, asked Defendant to get out of the truck, and independently asked about the strong odor. Defendant opened a box of cigarettes, pulled out a marijuana cigarette and a partially burned marijuana cigarette, told the agent that he smoked marijuana, that is what the agent smelled, and that was all he had. Defendant then consented to a canine search of the truck. When the dog alerted to the gas tank, Defendant voluntarily stated there was more marijuana in the tank. The agents discovered approximately twenty-nine pounds of marijuana in the gas tank. No more than six or seven minutes had elapsed between the time Defendant entered the checkpoint and when he told the agents there was more marijuana in the gas tank.
*115We are not concerned with the search. Defendant seems to concede that, once he displayed the marijuana cigarettes, probable cause existed to search. Additionally, Defendant consented to the search. In this case, we are concerned with what occurred from the time Defendant entered the main checkpoint to the time when he showed Howarth the marijuana cigarettes because this last fact provided probable cause to search the vehicle. See, e.g., State v. Capps, 97 N.M. 453, 456, 641 P.2d 484, 487 (officer had probable cause to search the ear after he smelled marijuana), cert. denied, 458 U.S. 1107, 102 S.Ct. 3486, 73 L.Ed.2d 1368 (1982).
We review the detention and questioning at secondary to determine whether it was supported by reasonable suspicion that Defendant was involved in criminal activity. See State v. Affsprung, 115 N.M. 546, 549, 854 P.2d 873, 876 (Ct.App.) (reasonable suspicion lower than probable cause standard), cert. denied, 115 N.M. 545, 854 P.2d 872 (1993). The evidence is viewed in the light most favorable to the district court’s ruling as we determine whether the law was correctly applied. State v. Galloway, 116 N.M. 8, 9, 859 P.2d 476, 477 (Ct.App.1993). We review as a matter of law the totality of the circumstances to determine whether the detention in this case was justified. Affsprung, 115 N.M. at 549, 854 P.2d at 876.
In the present case, the border patrol agents had drug enforcement authority as well as authority as immigration officers. Robinson had eleven years’ experience in law enforcement, including over three years as a border patrol agent, when Defendant was stopped. Robinson knew that deodorants are often used to mask the odor of illegal drugs or substances. He testified that the odor of the air fresheners from the truck was a lot stronger than he felt it should be, stronger than he had previously noticed in other vehicles. Indeed, when asked to rate the odor from the vehicle on a scale of one to ten when all the others had been fives, Robinson rated the odor as a nine. See United States v. Alvarado, 519 F.2d 1133 (5th Cir. 1975) (use of air freshener was factor in establishing articulable suspicion at border patrol checkpoint), cert. denied, 424 U.S. 911, 96 S.Ct. 1107, 47 L.Ed.2d 315 (1976); United States v. Solis-Serrano, 982 F.2d 530, 1992 WL 372405 (10th Cir.1992) (unpublished decision) (same); United States v. Sanchez-Valderuten, 11 F.3d 985, 989 (10th Cir.1993) (odor of deodorizer was factor in establishing reasonable suspicion after highway stop); State v. Alonzo, 587 So.2d 136, 140 (La.Ct.App.1991) (same); United States v. Stone, 866 F.2d 359, 362 (10th Cir.1989) (presence of Patchouli oil, which emits a strong odor, was factor in establishing reasonable suspicion); United States v. Jaime-Barrios, 494 F.2d 455 (9th Cir.) (observation of talcum powder, which smugglers often use to cover smell of marijuana, around trunks of vehicles was factor in establishing founded suspicion for stop), cert. denied, 417 U.S. 972, 94 S.Ct. 3178, 41 L.Ed.2d 1143 (1974); United States v. Reyna, 546 F.2d 103 (5th Cir.1977) (odor of air freshener was factor in establishing probable cause); United States v. Medina, 543 F.2d 553 (5th Cir.1976), cert. denied, 429 U.S. 1109, 97 S.Ct. 1144, 51 L.Ed.2d 563 (1977) (same); United States v. Gutierrez-Espinosa, 516 F.2d 249 (9th Cir.1975) (strong odor of car deodorizer was relevant to defendant’s knowledge of presence of marijuana in the vehicle).
In addition, Robinson noted that Defendant appeared very nervous when handing over the truck registration document. Nervousness during a routine checkpoint stop is more significant than nervousness when one’s vehicle is singled out from traffic for a police stop. See United States v. MartinezFuerte, 428 U.S. 543, 558, 96 S.Ct. 3074, 3083, 49 L.Ed.2d 1116 (1976) (motorist stopped at traffic checkpoint is much less likely to be frightened than is motorist stopped by a roving patrol). The highly unusual strength of the odor of the air freshener, together with Defendant’s nervousness, justified a brief extension of the detention of Defendant’s vehicle and questioning of Defendant.
In this regard, we emphasize that Defendant had already been subjected to a legal stop and brief detention. What is involved here is not the existence of reasonable suspicion necessary to justify the initial stop of a traveling motorist. The determination of whether reasonable suspicion justifies a de*116tention depends both on the probativeness of the articulable suspicious circumstances and the extent of the intrusion. See United States v. Chaidez, 919 F.2d 1193, 1198 (7th Cir.1990) (“Stops too intrusive to be justified by suspicion under Terry [v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968) ], but short of custodial arrest, are reasonable when the degree of suspicion is adequate in light of the degree and duration of restraint.”), certs. denied, 501 U.S. 1234, 111 S.Ct. 2861, 115 L.Ed.2d 1028, and 502 U.S. 872, 112 S.Ct. 209, 116 L.Ed.2d 167 (1991); accord United States v. Tilmon, 19 F.3d 1221, 1224 (7th Cir.1994); see Galloway, 116 N.M. at 10, 859 P.2d at 478 (“In determining the reasonableness of this detention, we emphasize the brief period of time involved.”). Cf. State v. Bolton, 111 N.M. 28, 42, 801 P.2d 98, 112 (Ct.App.) (a momentary extension of a previously lawful detention for the purpose of requesting permission to search is constitutionally permissible in certain circumstances), cert. denied, 111 N.M. 16, 801 P.2d 86 (1990).
We recognize that Defendant elicited testimony that Robinson had personally been involved in only five to ten cases during his time as a border patrol agent when a car was detained because of the smell of air freshener and contraband was found. Robinson could not estimate the number of vehicles that pass through the checkpoint with air fresheners, although there were “lots more” than five to ten. This testimony, however, does not invalidate Robinson’s reasonable suspicion of criminal activity based on his observation that the odor from this truck was much stronger than he usually encountered and his knowledge that air fresheners or other deodorizers are sometimes used to mask the odor of drugs. Nor does the fact that Robinson stated he had not personally used more than one air freshener at one time contradict his testimony that the smell seemed too strong even after he saw the two air fresheners in Defendant’s vehicle. The point was not that the smell seemed too strong given the number of air fresheners in the car; it was that the smell seemed too strong in light of the amount of ‘freshening’ used by other drivers, thus giving rise to an inference that the air fresheners served a purpose other than simply to improve the odor of the vehicle interior.
We recognize that the circumstances giving rise to Robinson’s suspicion do not strongly indicate criminal activity and are not necessarily inconsistent with innocent behavior. We disagree, however, with the dissent's apparent view that conduct consistent with innocent behavior cannot establish reasonable suspicion. To say that conduct is not consistent with innocent behavior is to say that the conduct conclusively establishes guilt. That is scarcely the test for reasonable suspicion, or even probable cause. The United States Supreme Court has repeatedly pointed out that conduct consistent with innocence may establish reasonable suspicion and probable cause. See United States v. Sokolow, 490 U.S. 1, 9-10, 109 S.Ct. 1581, 1586-87, 104 L.Ed.2d 1 (1989). “[Sjimply because certain conduct may be construed as consistent with innocent behavior does not mean that this conduct may not form the basis for reasonable suspicion. In many cases a police officer, familiar with the salient characteristics of a particular type of criminal activity, may be able to ‘perceive and articulate meaning in given conduct which would be wholly innocent to the untrained observer.’ Brown v. Texas, 443 U.S. 47, 52 n. 2 [99 S.Ct. 2637, 2641 n. 2, 61 L.Ed.2d 357] (1979).” United States v. Gomez, 776 F.2d 542, 548 (5th Cir.1985). The issue is whether the observation of the conduct “warranted further investigation.” Terry v. Ohio, 392 U.S. 1, 22, 88 S.Ct. 1868, 1880, 20 L.Ed.2d 889 (1968). The circumstances present here raised a substantial question regarding Defendant’s behavior, and the border patrol agents were warranted in briefly questioning Defendant to resolve that question. See Galloway, 116 N.M. at 9-10, 859 P.2d at 477-78; United States v. Ludlow, 992 F.2d 260, 264-65 (10th Cir.1993) (border patrol agents had reasonable suspicion that defendant was committing a crime because: defendant did not roll the driver’s window all the way down, raising a suspicion of trying to hide an odor; defendant was nervous, perspiring under his nose and looking all around; defendant could not find the car registration, and the car did not belong to him). Cf. United States v. *117 Fernandez, 18 F.3d 874, 881 (10th Cir.1994) (state trooper who pulled defendant’s truck over for a traffic violation and excessively tinted windows did not have a reasonable suspicion to continue the detention after issuing the traffic citation).
Judge Flores’ dissent relies on State v. Estrada, 111 N.M. 798, 810 P.2d 817 (Ct.App.1991). In that case, we held that an out-of-place spare tire, alone, was not such a suspicious circumstance as would justify the continuing detention to which the defendant was subjected. Id. at 802, 810 P.2d at 821. We did note in that opinion, however, the lack of suspicious factors such as nervousness or other unusual behavior. We also noted the absence of any evidence of experience of the agents with spare tires that would make the tire in that case an indicator of illegal conduct. Id. Here, we have both nervousness and experience with the use of air fresheners to mask the odor of unlawful drugs. Finally, and perhaps most significantly for this case, we said in Estrada that although the observation of the tire could not justify the particular detention, “the agent’s observation regarding the spare tire could justify further questioning.” Id. That is precisely what happened here.
The issue of reasonable suspicion was a question for the lower court to resolve, and it resolved that question against Defendant. Our function is to view the evidence in a light favorable to the district court’s ruling to determine if the law was correctly applied. We hold it was.
We affirm the district court’s order denying Defendant’s motion to suppress evidence.
IT IS SO ORDERED.
HARTZ, J., concurs.
BENNY E. FLORES, Judge (dissenting).