
902 A.2d 127 (2006)
Robert J. HOWARD, Appellant,
v.
UNITED STATES, Appellee.
No. 05-CM-221.
District of Columbia Court of Appeals.
Argued June 7, 2006.
Decided July 6, 2006.
*128 Dennis M. Hart, Washington, DC, appointed by the court, for appellant.
John W. Borchert, with whom Kenneth L. Wainstein, United States Attorney, and Roy W. McLeese III, and Margaret Sewell, Assistant United States Attorneys, were on the brief, for appellee.
Before WASHINGTON, Chief Judge, REID, Associate Judge, and KING, Senior Judge.
*129 REID, Associate Judge:
After a bench trial, appellant Robert J. Howard was convicted of one count of unlawful possession of a controlled substance (marijuana), in violation of D.C.Code § 48-904.01(d) (2001). He filed a timely notice of appeal challenging the trial court's denial of his motion to suppress evidence, the sufficiency of the evidence, and the trial court's denial of his motion to require the government to produce for examination at trial the chemist who prepared the chemical analysis of the substances which the police seized from his person and from the ground. We affirm the judgment of the trial court and hold (1) that the trial court properly denied Mr. Howard's motion to suppress evidence, and that the evidence was sufficient beyond a reasonable doubt to convict him of possession of a controlled substance; and (2) that Mr. Howard was afforded a statutory opportunity to confront the chemist at trial, but waived that right.

FACTUAL SUMMARY
During a hearing on Mr. Howard's motion to suppress, the government presented evidence showing that on February 6, 2004, around 10:50 p.m., Officer James Craig, a seven-year veteran of the Metropolitan Police Department ("MPD") and a member of the narcotics tactical unit, was on duty at an observation post in the 1200 block of Stevens Road (in the Southeast quadrant of the District of Columbia), "one of the largest open-air drug markets for the sales of marijuana in the District of Columbia," located in the Barry Farms Housing Complex. Officer Craig "was in the observation post for approximately two to three minutes." During that time he watched and listened as a man (later identified as Mr. Howard), who was wearing a black jacket and dark-colored pants, "attempt[ed] to flag down cars yelling, Hey, hey, right here, right here" and "waving his arms as cars would drive by." In light of his experience, gained from "approximately five hundred observation post[ ]" operations, Officer Craig concluded that "individuals in open-air drug markets [who] wave their hands and yell at cars passing by . . . [are] attempting to stop vehicles in order to sell narcotics." After "a couple of minutes[,]" Officer Craig's position was "compromised" when a passerby saw him. Consequently, Officer Craig used his radio to alert MPD Officer Eric Siebert,[1] who also was working in the Stevens Road area as part of an arrest team. Officer Craig told Officer Siebert that he should "move in and make contact with" Mr. Howard, described then by Officer Craig as "a black male wearing a black jacket and dark-colored pants yelling at cars as they were going by, attempting to flag them down." "[D]ue to [his] experience especially in an open-air drug market," Officer Siebert recognized that "if you're flagging down numerous vehicles[,] you're attempting to stop them to sell drugs." Officer Craig kept Mr. Howard in sight while he directed Officer Siebert (and Officer Matthew Daly) to the place where Mr. Howard was standing.
When Officer Siebert arrived on the scene in his "tactical uniform" (with a vest, badge and belt, and a "jacket underneath [his] vest that had MPD on the sides"), he saw Mr. Howard, who "was in the 1200 block of Stevens . . .; pretty much at the cross section of the alley . . . and Stevens Road." Another person stood "approximately 10 or 15 feet away from [Mr. Howard]," but Officer Siebert did not think they were "directly together." When Mr. Howard saw Officer Siebert, "[h]e quickly walked up Stevens Road towards Wade *130 Road."[2] Officer Siebert "asked him to stop," and as he approached Mr. Howard, the officer "saw four ziplock bags of marijuana. . . on the sidewalk." The bags were located "where [Mr. Howard] was standing."[3] Mr. Howard stopped, as requested, and Officer Siebert took him "over to where [Officer Daly] . . . had another individual stopped." Mr. Howard did not respond to Officer Siebert's question whether "he had any weapons on him." When the officer posed the question a second time and received no response, he "conducted a pat down of [Mr. Howard] for weapons." During the pat down, Officer Siebert "felt a texture consistent, from [his] experience, with ziplocks of marijuana." He removed the ziplocks and they later tested positive for marijuana.
During cross-examination of both officers, defense counsel sought to cast doubt on whether Mr. Howard was involved in any criminal activity, and whether he was the person that Officer Craig saw flagging down cars. Officer Craig acknowledged that he never saw Mr. Howard "sell anyone drugs" or "engage in any criminal activity"; nor did he remember providing information to Officer Siebert concerning Mr. Howard's height, weight or age. Officer Craig also reiterated that he was "sixty feet" away from Mr. Howard, and revealed that he was monitoring one other individual at the same time, but could not remember what that person was wearing. Officer Siebert said he did not see who dropped the ziplock bags that were on the ground. He recognized Mr. Howard as the person described in the radio transmission he received because he was "tall," there were "only two people . . . wearing all dark clothing," and when he saw Mr. Howard, Officer Craig sent a message to him that "that's the one."
The trial court found that the police had reasonable articulable suspicion to stop Mr. Howard, and soon thereafter had probable cause to arrest him and to search him incident to the lawful arrest:
I think there is articulable suspicion to stop Mr. Howard based . . . only on the fact that it's an open-air market and that he's waving his hands, saying "hey, hey, right here," trying to flag down a number of cars over [a] several minute period. I think that there was probably a crime. I find legally that there is reasonable articulable suspicion to stop him. But . . . even if there isn't . . . the frisk is not in any way a product of the stop, the frisk is the product of the observation of the drugs on the ground at his feet, combined with the other facts. . . .
And I also find that the drugs in the precise place where the defendant was at the time Officer S[ie]bert came into the block, coupled with the high drug area and the fact that the defendant was flagging down cars, is sufficient to create probable cause for the officers to arrest him, once there is probable cause, they can obviously search incident [to] that arrest. . . .
And I think a second ground for the frisk, even where probable cause is not sufficient, which I believe it is[,] . . . is the facts that I have mentioned, the drugs at his feet, the fact that he's flagging down [cars] gives the impression that he's a drug seller, coupled with his refusal to respond [to] the question, twice repeated on whether he had any weapons on him. . . . Therefore, he was entitled to remove [the ziplocks from *131 Mr. Howard's person,] and again that Terry frisk is really a secondary rationale for the search rather than the princip[al] one, which I believe is based on the probable cause, so I would deny [the] motion to suppress.
At trial, the judge incorporated the testimony given during the suppression hearing. Officer Siebert's additional testimony focused on the procedures he followed in processing the ziplock bags found at the scene. With respect to those procedures, Mr. Howard moved for judgment of acquittal on the ground that there was a "discrepancy between the lab numbers . . . [which] would indicate that there's a question as to whether or not these are the same drugs that . . . in fact were allegedly taken from Mr. Howard and the Government has not proven constructive possession from the bags  the bags that were allegedly on the ground." The trial court denied the motion.
Mr. Howard testified in his own behalf. He denied the account of events given by the officers, and maintained that he had large holes in the pockets of his jacket that would make it impossible to retain ziplocks in them. He also denied having any drugs on the day in question. He claimed that the police did not find any ziplock bags on his person, and that he was arrested only because of the bags found on the ground. He stated that he was in the 1300 block of Stevens Road because his grandmother lived there. He believed the police fabricated the charge against him because he "beat" another possession charge after Officer Daly had arrested him in a prior year, and Officer Daly "had a terrible disposition towards [him]." In rebuttal, Officer Siebert testified that Mr. Howard had a hole in the pocket from which he removed the ziplock bags, but he demonstrated that the hole was only about three inches by one inch, and was "near the back of the jacket [but] the drugs were near the front."
At the conclusion of the trial, the judge incorporated his earlier findings relating to the denial of the suppression motion. In addition, he determined that Officer Siebert's testimony "seemed entirely credible" but that both on direct and cross-examination, "Mr. Howard's testimony was not credible" and was "evasive"; that Mr. Howard possessed the six ziplock bags found on his person and the four on the ground where he had been standing; and that the marijuana found on the ground and that discovered in Mr. Howard's jacket pocket "matched." Therefore, the court concluded that Mr. Howard "did possess both the [m]arijuana in his pocket and the [m]arijuana on the ground, and [found] him guilty of the crime of possession of [m]arijuana."

ANALYSIS

The Suppression Issue
Mr. Howard contends that the trial court should have granted his Fourth Amendment motion to suppress evidence essentially because the police did not have reasonable, articulable suspicion to effect a stop under Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968), and that the police did not have a valid basis for the subsequent frisk of his person and seizure of the ziplock bags. The government argues that "the trial court properly concluded that the initial stop of appellant was supported by reasonable articulable suspicion," and that "[t]he trial court was also correct in finding that, once Officer S[ie]bert saw four zip-lock bags of suspected contraband on the ground where [Mr. Howard] had just been standing while flagging down cars, the police had probable cause to arrest [him] and could search him incident to his arrest."
*132 "[O]ur standard of review for a trial court's ruling on a motion to suppress tangible evidence requires that the facts and all reasonable inferences therefrom must be viewed in favor of sustaining the trial court's ruling." In re T.H., No. 05-FS-306, 898 A.2d 908, 912, 2006 D.C.App. Lexis 210, at *9 (citing United States v. Watson, 697 A.2d 36, 38 (D.C.1997)) (quoting Holt v. United States, 675 A.2d 474, 478 (D.C.1996) (internal quotation marks omitted)); see also Peay v. United States, 597 A.2d 1318, 1320 (D.C.1991) (en banc). "While factual findings will not be disturbed if supported by substantial evidence, conclusions of law are reviewed de novo." T.H., supra, 898 A.2d at 912, 2006 D.C.App. Lexis, at *9 (citing Holt, supra, 675 A.2d at 478) (internal quotation marks omitted). This court must "ensure that the trial court has a substantial basis for concluding that no constitutional violation occurred." Thompson v. United States, 745 A.2d 308, 312 (D.C.2000) (other citation and internal quotation marks omitted).
"To conduct a brief, investigatory stop of a person in keeping with the Fourth Amendment, a police officer must have a reasonable, articulable suspicion that criminal activity may be afoot." Wilson v. United States, 802 A.2d 367, 369 (D.C.2002) (citing Terry, supra, 392 U.S. at 30, 88 S.Ct. 1868) (other citation omitted). "While reasonable suspicion is a less demanding standard than probable cause and requires a showing considerably less than preponderance of the evidence, the Fourth Amendment requires at least a minimal level of justification for making the stop." Id. (citing Illinois v. Wardlow, 528 U.S. 119, 123, 120 S.Ct. 673, 145 L.Ed.2d 570 (2000)). And, the police must have more than an "inchoate and unparticularized suspicion or hunch of criminal activity." Id. (citing Terry, 392 U.S. at 27, 88 S.Ct. 1868) (internal quotation marks omitted).
Mr. Howard maintains that "[w]a[ ]ving at passing cars, even in a drug activity neighborhood, has not yet been elevated to the red flag status sufficient for a Terry stop," while the government argues that Mr. Howard's "conduct in flagging down cars in an open-air market . . . by itself furnish[ed] the police with reasonable articulable suspicion to support a stop." If this conduct was not sufficient by itself, the government contends, the added factors of Mr. Howard quickly walking away when he saw Officer Siebert in his MPD tactical uniform and "the high-drug area" formed the justification for the stop.
In Wardlow, supra, the Supreme Court of the United States declared that: "An individual's presence in an area of expected criminal activity, standing alone, is not enough to support a reasonable, particularized suspicion that the person is committing a crime." Id. at 124, 120 S.Ct. 673 (citing Brown v. Texas, 443 U.S. 47, 99 S.Ct. 2637, 61 L.Ed.2d 357 (1979)). Nevertheless, presence in a high crime area is a factor to be considered in determining whether a police officer had reasonable, articulable suspicion. As the court said: "[O]fficers are not required to ignore the relevant characteristics of a location in determining whether the circumstances are sufficiently suspicious to warrant further investigation[;]. . . . [T]he fact that the stop occurred in a `high crime area' [is] among the relevant contextual considerations in a Terry analysis." Id. (citation omitted). In the case before us, Mr. Howard not only was in an area known for illegal drug transactions, but the police saw him flagging down cars and yelling "hey, hey, right here, right here." Both Officers Craig and Siebert testified that, based on their experience, the act of flagging and waving down cars in an open-air *133 drug market represents an effort to sell drugs.
Wardlow also recognized that "unprovoked flight upon noticing the police" or "nervous, evasive behavior" such as "[h]eadlong flight . . .[,] the consummate act of evasion . . .," may support reasonable, articulable suspicion. Wardlow, supra, 528 U.S. at 124, 120 S.Ct. 673 (citations omitted). Here, added to Mr. Howard's presence in a high crime area and his flagging and waving actions designed to get buyers for drugs, is the fact that he "quickly walked" up the road when he saw Officer Siebert, who was wearing his tactical uniform  vest, police badge, belt, and a jacket underneath his vest with the letters MPD on the sides. Although he did not run, his act of "quickly walking" away upon seeing the police officer, constituted "evasive" behavior. Based upon the foregoing actions of Mr. Howard, we hold that Officer Siebert had "reasonable, articulable suspicion that criminal activity [might] be afoot," Wilson, supra, 802 A.2d at 369 (citing Terry, supra, 392 U.S. at 30, 88 S.Ct. 1868) (other citation omitted), and his Terry investigative stop was justified.
Furthermore, Officer Siebert's discovery of the ziplock bags on the ground where Mr. Howard had been standing, which he described as "pretty much at the cross section of the alley . . . and Stevens Road," together with the factors discussed above, established probable cause to arrest the appellant. And, the search of Mr. Howard's person, which yielded ziplock bags that "matched" those on the ground, was valid as a search incident to a legal arrest. Holt, supra, 675 A.2d at 481 ("Once the police make a lawful arrest, they may search the arrestee's person and the area within his immediate control, in order to prevent the arrestee from gaining possession of a weapon or destructible evidence.").[4] In short, the trial court properly denied Mr. Howard's motion to suppress evidence, and the evidence was sufficient beyond a reasonable doubt to convict him of unlawful possession of a controlled substance (marijuana).

The DEA Chemist Issue
Mr. Howard argues that "[b]y allowing the government to make its case without the live testimony of [the DEA chemist] who performed . . . [the] analysis [of the substance in the ziplock bags found on the ground], the trial court improperly shifted the burden of proof and denied [Mr. Howard] his Confrontation Clause rights" under the Sixth Amendment. He relies on Crawford v. Washington, 541 U.S. 36, 124 S.Ct. 1354, 158 L.Ed.2d 177 (2004) which he maintains "trumped" our decision in Howard v. United States, 473 A.2d 835 (D.C.1984). The government argues that D.C.Code § 48-905.06,[5] which *134 establishes the procedures for the admission of a chemist's report into evidence, was not invalidated by Crawford; but that "[e]ven if [the chemist's report] is a `testimonial' statement, D.C.Code § 48-905.06 does not violate the Confrontation Clause." The government also contends that, "[b]ecause he never contested the chemist's findings at trial, [Mr. Howard] suffered no actual prejudice from his inability to have the government present the chemist's findings via live testimony."
In October 2004, the government filed a notice of compliance with § 48-905.06, stating that: "The United States of America, by its attorney, the United States Attorney for the District of Columbia, herewith is serving upon the defense and filing with the Court copies of the official reports of chain of custody and of analysis of a controlled substance relevant to this case, together with a certificate of legal custody." Section 48-905.06 specifies that "the official report of chain of custody and of analysis of a controlled substance . . . shall be admissible in evidence as evidence of the facts stated therein and the results of that analysis." The statute also provides that if a defendant wants to cross-examine the chemist who prepared the reports, "the defendant or his or her attorney [may] subpoena[ ] the chemist for examination. . . ." And, "the subpoena shall be without fee or cost. . . ." The notice filed by the government requested that the defense follow specified procedures "should [it] elect to subpoena the chemist for examination. . . ."
The defense was silent about the government's notice of compliance with § 48-905.06 until February 1, 2005, two days before trial, when it filed a motion in limine to exclude the report of analysis, known as the DEA-7 (Certified Report of Controlled Substance Analysis Prepared By the Drug Enforcement Administration), asserting that Mr. Howard's rights under the Confrontation Clause would be violated if the report was admitted into evidence. The government opposed the motion. On February 3, 2005, defense counsel argued that the chemist's report is "testimonial evidence and the defense should have the ability to cross-examine" the chemist; and further, that the burden was on the government to produce the chemist for examination. The government argued that:
[A]s far as the confrontation clause goes, there is a self-help provision in the statute. All the defendant has to do is subpoena the chemist and [he will] come and testify and . . . can be crossed on all these issues, that's a simple matter. [The defense] had plenty of time to do that and somebody did not avail [himself] of that opportunity.
The trial court took the position that Howard had not been overruled, and denied the defense motion to exclude the DEA-7.
Mr. Howard never challenged the results of the chemist's analysis. He objected only to the admission of the chemist's worksheet, which was excluded, but not *135 the certification showing 10 grams of a measurable amount of marijuana in the six ziplock bags removed from Mr. Howard's jacket pocket by Officer Siebert. Where there is no challenge to the results, the spirit of § 48-905-06 does not mandate that the chemist be called to testify. In that regard, we said in Howard, supra:
Supported by the `business records' exception to the hearsay rule, D.C.Code [§ 48-905.06] was enacted to `relieve . . . chemists from the requirement of making. . . personal appearances' at trials where the results of chemical analyses are not in dispute.
Id. at 838 (quoting COUNCIL OF THE DISTRICT OF COLUMBIA, REPORT OF COMM. ON JUDICIARY, "D.C. Uniform Controlled Substances Act of 1981" (April 18, 1981)). Not only did Mr. Howard not contest the results of the chemist's analysis, but he also did not subpoena the chemist for examination at trial, as § 48-905.06 permits.
Under these circumstances, we do not need to address whether the DEA-7 is "testimonial." The Supreme Court observed in Crawford that "[t]estimonial statements of witnesses absent from trial have been admitted only where the declarant is unavailable, and only where the defendant has had a prior opportunity to cross-examine." 541 U.S. at 38, 124 S.Ct. 1354 (footnote omitted). Thus, "[w]here testimonial evidence is at issue . . ., the Sixth Amendment demands what the common law required: unavailability and a prior opportunity for cross-examination." Id. at 53, 124 S.Ct. 1354. Here, there is no indication in the record that the chemist who performed the chemical analysis admitted at Mr. Howard's trial was not available to present himself for examination. Moreover, nothing in § 48-905.06 places the burden on the government to present the chemist for cross-examination, where the defense chooses not to subpoena the chemist. Indeed, the statute singles out "the defendant, or his or her attorney" as the person who will subpoena the chemist, and even mandates that "the subpoena shall be without fee or cost."
Had the defense served a subpoena on the chemist, as the statute permits, the government could have presented him in its case in-chief, and the chemist then would have been available for cross-examination by the defense. Under the circumstances of this case, we hold that Mr. Howard waived his right to confront the chemist.
Accordingly, for the foregoing reasons, we affirm the judgment of the trial court.
So ordered.
NOTES
[1]  Officer Siebert's last name also appears in the record incorrectly as "Seibert."
[2]  The other person on the street also walked away, and was apprehended by Officer Siebert's partner.
[3]  Officer Craig did not see Mr. Howard drop anything.
[4]  We need not reach Mr. Howard's claim that the evidence was insufficient to show that he constructively possessed the ziplock bags on the ground that contained marijuana. Since he was convicted on one count of unlawful possession of a controlled substance, and because the trial court credited the testimony of Officer Siebert that he removed six ziplock bags containing marijuana from Mr. Howard's jacket pocket, Mr. Howard had actual possession of those bags and that was sufficient beyond a reasonable doubt to support the possession charge. See Griffin v. United States, 502 U.S. 46, 112 S.Ct. 466, 116 L.Ed.2d 371 (1991); Smith v. United States, 809 A.2d 1216, 1221-22 (D.C.2002). In addition, given our analysis, we need not address Mr. Howard's contention that the trial court erred by invoking the "plain feel" doctrine to justify the search of his person.
[5]  D.C.Code § 48-905.06 (2001) provides:

In a proceeding for a violation of this chapter, the official report of chain of custody and of analysis of a controlled substance performed by a chemist charged with an official duty to perform such analysis, when attested to by that chemist and by the officer having legal custody of the report and accompanied by a certificate under seal that the officer has legal custody, shall be admissible in evidence as evidence of the facts stated therein and the results of that analysis. A copy of the certificate must be furnished upon demand by the defendant or his or her attorney in accordance with the rules of the Superior Court of the District of Columbia or, if no demand is made, no later than 5 days prior to trial. In the event that the defendant or his or her attorney subpoenas the chemist for examination, the subpoena shall be without fee or cost and the examination shall be as on cross-examination.
