Jean Taylor appeals the judgment of conviction and sentence entered against her on one count of knowingly and intentionally manufacturing marijuana in violation of 21 U.S.C. §§ 841(a)(1), 841(b)(1)(B) and 18 U.S.C. § 2. We affirm.

On the morning of July 17, 1991, Robert Hutchings, Jr., a special agent of the Maine Bureau of Intergovernmental Drug Enforcement ("BIDE"), spoke with a confidential informant who reported that he recently had visited appellant Taylor and her husband at property in Levant, Maine, upon which the Taylors resided in separate mobile homes. The informant observed several large marijuana plants (up to 4 feet tall) growing in appellant's vegetable garden and around the perimeter of her mobile home, several hundred marijuana seedlings (5 to 6 inches tall) growing in milk cartons and crates and awaiting transplantation to nearby woods, and an "unusual amount" of zip lock storage bags inside appellant's residence. During one visit, appellant told the informant she was concerned because she had started more seedlings than she could tend.

The same day he received the tip from the informant, Agent Hutchings consulted the affidavit submitted in support of a 1986 search warrant application, in which another officer attested that he had purchased marijuana from Taylor on two occasions and personally observed marijuana plants growing on her property. A local drug task force report noted that Taylor had pled guilty to two counts of marijuana trafficking in October 1986. Incorporating this evidence into an affidavit, Hutchings obtained a state court search warrant which was executed later that day. Appellant ultimately was charged in the United States District Court for the District of Maine with manufacturing marijuana in violation of federal law.

The district court denied appellant's motion to suppress the physical evidence (marijuana plants and drug paraphernalia) based on an alleged absence of probable cause to support the search warrant. Appellant contends that Agent Hutchings' sworn statements vouching for the informant's reliability were conclusory and that the tips provided by the informant were inadequately corroborated.

The sufficiency of a search warrant affidavit is appraised against well-established criteria:

The task of the issuing magistrate is simply to make a practical, common-sense decision whether, given all the circumstances set forth in the affidavit before him, including the "veracity" and "basis of knowledge" of persons supplying hearsay information, there is a fair probability that contraband or evidence of a crime will be found in a particular place. And the duty of a reviewing court is simply to ensure that the magistrate had a "substantial basis for ... conclud[ing]" that probable cause existed.

United States v. Caggiano, 899 F.2d 99, 102 (1st Cir.1990) (quoting Illinois v. Gates, 462 U.S. 213, 238-39, 103 S. Ct. 2317, 2332, 76 L. Ed. 2d 527 (1983)) (citations omitted); see also United States v. Ventresca, 380 U.S. 102, 108, 85 S. Ct. 741, 745-46, 13 L. Ed. 2d 684 (1965). The reviewing court does not undertake de novo review, but accords "great deference" to the probable cause determination. United States v. Ciampa, 793 F.2d 19, 22 (1st Cir.1986) (citation omitted).

The Hutchings affidavit tersely attests that the informant "has provided reliable information [to law enforcement officials] in the past." Standing alone, so conclusory a statement might not provide an issuing magistrate with the requisite " 'substantial basis for concluding that probable cause existed.' " Caggiano, 899 F.2d at 103 (quoting Gates, 462 U.S. at 238-39, 103 S.Ct. at 2332). On the other hand, an informant's reliability need not invariably be demonstrated through a detailed narration of the information previously furnished to law enforcement--for example, by listing the number or names of persons arrested or convicted as a consequence of the informant's prior assistance. Rather, the affidavit may disclose an adequate basis for evaluating the informant's veracity through the very specificity and detail with which it relates the informant's first-hand description of the place to be searched or the items to be seized. Id. at 102-03 (reliability of information enhanced if details derived from informant's personal observation, rather than from hearsay) (citing Ciampa, 793 F.2d at 24). As was the case in Caggiano,1 the informant provided Agent Hutchings with a detailed description of the premises to be searched, including the exteriors and interiors of the Taylor residences, noting in particular the 400 to 500 marijuana seedlings being raised in milk cartons and crates at appellant's residence.

Continuing with the "totality of the circumstances" analysis mandated by Gates, we find no merit in appellant's contention that Hutchings conducted an inadequate or superficial follow-up investigation of the informant's tip. On the contrary, Hutchings promptly set out to corroborate the informant's tip by consulting official records relating to appellant's prior convictions for marijuana trafficking. These records indicated that appellant, five years earlier, admitted to another police officer that she intentionally cultivated marijuana on the same property, and later entered a guilty plea to a state trafficking charge. An affiant's knowledge of the target's prior criminal activity or record clearly is material to the probable cause determination. See United States v. Asselin, 775 F.2d 445, 446 (1st Cir.1985); United States v. Sumpter, 669 F.2d 1215, 1222 (8th Cir.1982). Moreover, the issuing magistrate properly may credit the experience and pertinent expertise of a law enforcement affiant in evaluating the authenticity of the informant's description of the target's modus operandi. See United States v. Soule, 908 F.2d 1032, 1040 (1st Cir.1990) (citing United States v. Ortiz, 422 U.S. 891, 897, 95 S. Ct. 2585, 2589, 45 L. Ed. 2d 623 (1975) ("[O]fficers are entitled to draw reasonable inferences from [ ] facts in light of their knowledge of the area and their prior experience....")). In the present case, the informant's detailed description of the location, manner and extent of the marijuana cultivation and the presence on the same premises of an unusually large number of zip lock plastic bags, cf. United States v. Desmarais, 938 F.2d 347, 352 (1st Cir.1991) (presence of plastic baggies supports reasonable inference of intent to distribute marijuana and hashish found on same premises), combined with Agent Hutchings' extensive experience as a law enforcement officer in Maine,2 plainly buttressed the informant-based indicia of probable cause. We accordingly conclude, based on the totality of the circumstances, that the Hutchings affidavit provided a substantial basis for the issuing judicial officer's practical, common-sense finding that there was a fair probability that evidence of a crime would be found on appellant's premises.

While a search team executed the warrant, Agent Hutchings arrested appellant and placed her in the back seat of a police vehicle. Hutchings testified that he gave appellant no Miranda warnings because he did not intend to ask her any questions. At some point during the trip to the county jail, appellant initiated conversation by asking: "Why is this happening to me?" Hutchings replied: "You can't be growing dope on your property like that." Taylor responded: "If you had waited and come next week, you'd have only gotten half the plants that you did[,] the way you do is you pull the male plants early." She added that she was growing the marijuana plants for treatment of a medical condition. As appellant was speaking, Hutchings turned on the overhead light in the vehicle and, without stopping the vehicle, wrote appellant's statements on a pad. Later, during "booking" at the county jail, appellant spontaneously repeated some of these statements to a deputy sheriff.

Miranda warnings must be given before a suspect is subjected to "custodial interrogation." United States v. Maguire, 918 F.2d 254, 262 (1st Cir.1990), cert. denied, --- U.S. ----, 111 S. Ct. 1421, 113 L. Ed. 2d 474 (1991).3 "Interrogation" includes not only the asking of direct questions but also means "any words or actions on the part of police (other than those normally attendant to arrest and custody) that the police should know are reasonably likely to elicit an incriminating response from the suspect." Rhode Island v. Innis, 446 U.S. 291, 301, 100 S. Ct. 1682, 1690, 64 L. Ed. 2d 297 (1980) (emphasis added).4 Since Hutchings' response to appellant's spontaneous inquiry was not interrogative, we must determine whether it nevertheless constituted the "functional equivalent." Id. at 302, 100 S.Ct. at 1690.5

Appellant argues that Hutchings intended to elicit an incriminating statement en route to the county jail. As evidence, she points to Hutchings' own testimony that suspects often engage in conversation or general banter while being transported to jail. More pointedly, she asserts that, when Hutchings' expectation was confirmed by appellant's inquiry, he deliberately narrowed his response by referring directly to the criminal charge for which appellant had just been arrested.

The "functional equivalence" test does not turn on the subjective intent of the particular police officer but on an objective assessment as to whether the police statements and conduct would be perceived as interrogation by a reasonable person in the same circumstances. See Arizona v. Mauro, 481 U.S. 520, 527, 107 S. Ct. 1931, 1935, 95 L. Ed. 2d 458 (1987); Innis, 446 U.S. at 301-02 n. 7, 100 S. Ct. at 1690 n. 7; cf. United States v. Soto, 953 F.2d 263, 265 (6th Cir.1992) (noting that the "[a]bsence of intent to interrogate, while not irrelevant, is not determinative of whether police conduct constitutes interrogation"). Although a different result might obtain were it established that the challenged police conduct was designed to elicit a response, see United States v. Vazquez, 857 F.2d 857, 863 (1st Cir.1988) (quoting Innis, 446 U.S. at 302 n. 7, 100 S. Ct. at 1690 n. 7), the mere fact that a police officer may be aware that there is a "possibility" that a suspect may make an incriminating statement is insufficient to establish the functional equivalent of interrogation. Mauro, 481 U.S. at 528-29, 107 S.Ct. at 1936-37.

Hutchings testified that he "might have anticipated that [appellant] would make some sort of statement in response to what [he] said," but because the entire conversation was so abruptly initiated by Taylor, and so transitory, he "wasn't thinking of what her next sentence was going to be or what she was even thinking." Tr. at 38-39. We think Hutchings' conduct indicates no premeditated or deliberate design, but evidences, at most, Hutchings' awareness that appellant might continue the conversation she spontaneously initiated. See, e.g., Innis, 446 U.S. at 303, 100 S.Ct. at 1690-91 (noting that police comments were part of "brief conversation" containing "a few offhand remarks"); Plazinich v. Lynaugh, 843 F.2d 836, 840 (5th Cir.1988) (noting brevity and informality of officer's statement to defendant as evidence of lack of "interrogation"), cert. denied, 488 U.S. 1031, 109 S. Ct. 841, 102 L. Ed. 2d 973 (1989).6

Nor can we agree that Hutchings' answer unresponsively "narrowed" appellant's inquiry, or designedly channeled her attention toward dangerous waters. Viewed objectively, appellant's initial inquiry ("Why is this happening to me?") was a direct request for an explanation as to why she was under arrest. Appellant would have us propound a rule that police officers may not answer direct questions, even in the most cursory and responsive manner. It might well be argued, however, that an officer's refusal to respond to such a direct question in these circumstances would be at least as likely to be perceived as having been intended to elicit increasingly inculpatory statements from a disconsolate suspect arrested moments before. Although we do not rule out the possibility that "interrogation" might occur as a consequence of a police officer's response to, or relentless pursuit of, this type of inquiry in other circumstances, cf., e.g., Harryman v. Estelle, 616 F.2d 870, 874 (5th Cir.) (relevant inquiry is whether officer's statement of "surprise," however posed, "could reasonably have had the force of a question ") (emphasis added), cert. denied, 449 U.S. 860, 101 S. Ct. 161, 66 L. Ed. 2d 76 (1980), in the present case appellant's inquiry was entirely spontaneous and the officer's answer was cursory and directly responsive. See United States v. Jackson, 863 F.2d 1168, 1172 (4th Cir.1989) (finding no "interrogation" where police officer responded to direct inquiry regarding reasons for defendant's arrest, made during conversation initiated by defendant); United States v. Crisco, 725 F.2d 1228, 1232 (9th Cir.) (holding that police officer's informational response to defendant who expressed general "bewilderment" at arrest was not "interrogation"), cert. denied, 466 U.S. 977, 104 S. Ct. 2360, 80 L. Ed. 2d 832 (1984); cf. Arizona v. Roberson, 486 U.S. 675, 687, 108 S. Ct. 2093, 2101, 100 L. Ed. 2d 704 (1988) (noting that, after defendant invokes Miranda rights, there is no "interrogation" if police merely "inform" defendant about an investigation of a second offense of which he is suspected).

We thus conclude that appellant's statement was not the product of custodial interrogation. Miranda v. Arizona, 384 U.S. 436, 478, 86 S. Ct. 1602, 1630, 16 L. Ed. 2d 694 (1966) ("Volunteered statements of any kind are not barred by the Fifth Amendment...").7C. Rational Basis for Drug Equivalency Ruling

The district court applied the drug equivalency standard prescribed in U.S.S.G. § 2D1.1(c): "in the case of an offense involving marijuana plants, if the offense involved 50 or more plants, [the court should] treat each plant as the equivalent of one kilogram of marijuana." Consequently, appellant was sentenced to ninety-nine months' imprisonment (offense level 28, criminal history category II), based on the 661 marijuana plants seized in and around her residence.

Appellant claims that section 2D1.1(c) is arbitrary and without a rational empirical basis; hence its application violates due process. She relies on expert testimony presented in the case of United States v. Osburn, 756 F. Supp. 571 (N.D.Ga.1991), to the effect that it is impossible to cultivate a marijuana plant whose yield would exceed one kilogram of marijuana.

We disagree with appellant that the equivalency standard is arbitrary. Congress reasonably may opt for a punitive deterrent against large-scale marijuana manufacturing operations which pose a greater threat than small-scale operations, and warrant exponentially enhanced punishment. See United States v. McMahon, 935 F.2d 397, 401 (1st Cir.1991) (" 'Congress intended to punish growers of marihuana by the scale or potential of their operation and not just by the weight [or size] of the plants seized at a given moment.' ") (citation omitted); see also United States v. Jordan, 964 F.2d 944, 947 (9th Cir.1992); United States v. Holmes, 961 F.2d 599, 601 (6th Cir.1992); United States v. Motz, 936 F.2d 1021, 1025-26 (9th Cir.1991).8 Even were we to conclude, however, that empirical evidence could undermine the constitutionality of § 2D1.1, a conclusion we need not consider, appellant not only failed to present evidence in support of such a claim but her borrowed empirical support has vanished.9 The district court's application of U.S.S.G. § 2D1.1 did not constitute error.

Affirmed.