Before Farrell and Reid, Associate Judges, and Mack, Senior Judge.
The opinion of the court was delivered by: Reid, Associate Judge
Appeals from the Superior Court of the District of Columbia (Hon. John H. Bayly, Jr., Trial Judge)
Appellants Troy Thompson and Tyrone D. Hall challenge their convictions for unlawful possession of a controlled substance (cocaine), in violation of D.C. Code § 33-541 (d) (1998). *fn1 Charged in the same indictment, which resulted in the convictions of Thompson and Hall, were co-defendants Garland J. Lathan and William J. Corum, Jr. Thompson contends that the trial court erred by: (1) allowing the government to introduce additional evidence after the parties made closing arguments during the hearing on pre-trial motions; *fn2 and (2) denying his motion for suppression of physical evidence. Hall argues that the trial court erred by denying his motions: (1) to suppress evidence; and (2) to sever his trial from that involving a drug transaction between co-defendants Lathan and Corum. We affirm.
The record on appeal reveals the following events which occurred on January 31, 1996, around 9 p.m. in the 600 block of Columbia Road, N.W., in the District of Columbia. *fn3 Metropolitan Police Department ("MPD") Officer Patrick Alan Goodwin was on a surveillance assignment at an observation post in an FBI van in the 500 block of Columbia Road, N.W., because of "ongoing drug complaints in that area." Officer Goodwin "used the telescope feature that was located in the van" to observe the premises at 600 to 606 Columbia Road. His observation post was about 80 yards from co-defendant Lathan. Officer Goodwin watched Lathan sit on the porch of 602 Columbia Road in the cold for about twenty minutes. At about 9:07 p.m. Officer Goodwin, who at the time had been with the MPD for about six years and assigned to the vice unit for about a year and a half, saw a two-door Nissan drive into the area. The vehicle bore District license tags. The driver of the car exited the vehicle while a passenger remained inside. Officer Goodwin could not describe the passenger. Lathan left the porch to meet the driver, later identified as Thompson. The two men conversed and "walk[ed] towards the mouth of the alley right beside 600 Columbia Road." The area was illuminated by three "high crime [District] lights." The men stopped. "Lathan then reached down and picked up an object and handed it to [Thompson], [who] then in return gave  Lathan an undetermined amount of currency." The object was "small" but Officer Goodwin could not see specifically what it was. Lathan put the currency in his pocket and proceeded back to the porch of 602 Columbia Road, N.W. Thompson returned to his vehicle and "display[ed] the object . . . to the passenger," later identified as Hall. The Nissan moved toward Georgia Avenue.
Officer Goodwin gave a "lookout" over "a hand[-]held radio" to the other officers assigned to the surveillance unit. He stated at trial: "I gave a lookout for the buyer which was a Black male wearing a black jacket and blue[-]jeans. He was the driver of the vehicle. I also gave the tag number of the vehicle . . . ." Officer Goodwin acknowledged that he "never gave any type of description of the passenger" in the Nissan, and that he never saw the passenger. *fn4 An arrest team stopped the Nissan "within thirty seconds" of the "lookout" given by Officer Goodwin.
Before the arrest unit could seize Lathan, Officer Goodwin observed him engage in another transaction with a Black male in a two-door, blue BMW. Lathan again left the porch of 602 Columbia Road to meet the driver of the car. They proceeded to the same alley. Lathan "went down again in the same area of the first transaction and picked up an object and gave it to [the driver of the BMW]." The driver, later identified as Corum, returned to his car and drove into the 700 block of Columbia Road where he was stopped. Eventually, Lathan was apprehended.
Officer Eric Espinosa, who at the time of the incident had been a police officer for about eight years and who then was assigned to the vice unit, testified at trial that he and two other officers who were with him (Officers Timlick and Grant), received a "lookout . . . for a dark colored Nissan [with a] subject . . . wearing a dark colored coat . . . ." He did not recall whether the "look out" broadcast included the license number of the Nissan. About "a minute" later, the officers stopped the Nissan. "As [Officer Espinosa] approached the vehicle, [he] observed the driver handing an object to the passenger . . . ." Officer Espinosa subsequently arrested Thompson. On cross-examination, Officer Espinosa stated: "I observed the driver handing with his right hand a small object to the person on the passenger's side as I approached the vehicle." When asked whether or not that was all he saw, Officer Espinosa responded: "Yes." He did not remove the object from the Nissan. He did not see any brown paper. *fn5
Officer Cardis Timlick, a member of the team that arrested Thompson and Hall on January 31, 1996, stated at trial that "Investigator Goodwin gave a lookout of . . . a brown Nissan Sentra. . . ." *fn6 Within "a minute or two" of the "lookout," Officer Timlick "saw the Nissan Sentra going west on Columbia Road in the 700 block." He saw no other dark Nissan in the area. He and the other officers "stopped the vehicle based on a lookout of . . . Thompson." As "[he] approached the passenger's side [of the Nissan] . . . ,  Thompson was observed handing something in the form of a small object to  Hall." *fn7 Furthermore, Hall "was observed dropping a black [z]iploc containing a white rock substance to the floorboard of the vehicle." Officer Timlick "retrieved" the object and it field tested positive for cocaine. *fn8 On cross-examination, Officer Timlick testified that he arrested Hall because: "I observed him dropping a [z]iploc containing a white rock substance to the floorboard of the vehicle in which he was sitting." Later, Officer Timlick stated: "I saw him drop something and when I looked to see what he dropped, it was a black [z]iploc containing a white rock substance." He "did not arrest [Hall] until the field test was conducted which  tested positive for cocaine." Furthermore, Officer Timlick declared: "Mr. Thompson was the one we wanted to stop in the vehicle. Mr. Hall was not the one we wanted to get involved in this transaction at all up until I observed him while we were approaching the vehicle to stop Mr. Thompson and no lookout was for a brown paper bag . . . ." Nor did Officer Timlick ever see or recover a brown paper bag from the Nissan. Still later on cross-examination, Officer Timlick asserted: "I never said I saw [Thompson] give [Hall] a black [z]iploc. I stated I saw [Thompson] give [Hall] something in the shape of a small object."
The final government witness at trial, Detective Charles Culver, gave expert testimony at trial concerning, inter alia, the distribution of drugs. He indicated that a person selling drugs "might use a stash" to hide the drugs, to avoid discovery of the drugs on their person, and to preclude robbery "by other criminals." None of the defendants presented any witnesses.
Both Thompson and Hall contend that the trial court erred by denying their motions to suppress evidence. Our review of the denial of a suppression motion "is limited." Lawrence v. United States, 566 A.2d 57, 60 (D.C. 1989). "Essentially our role is to ensure that the trial court has a substantial basis for concluding that no constitutional violation occurred." Id. (citing Goldston v. United States, 562 A.2d 96, 98 (D.C. 1989)). Moreover, "in reviewing a trial court order denying a motion to suppress, the facts and all reasonable inferences therefrom must be viewed in favor of sustaining the trial court ruling." Peay v. United States, 597 A.2d 1318, 1320 (D.C. 1991) (en banc) (citing Nixon v. United States, 402 A.2d 816, 819 (D.C. 1979)). "We must accept the trial judge's findings of evidentiary fact and his [or her] resolution of conflicting testimony." Brown v. United States, 590 A.2d 1008, 1020 (D.C. 1991) (citing Lawrence, 566 A.2d at 60).
Thompson asserts "that the police seized him without probable cause or reasonable suspicion." Hall maintains, primarily, that "an exchange or sale of an unknown object, standing alone, does not justify a police stop or seizure of the suspect or of an automobile"; and that "[i]f what the police saw in the 600 block of Columbia Road did not provide probable cause or reasonable belief that a crime had been committed[,] there was no legal justification[,] under any scenario[,] for the subsequent stop/seizure of the automobile." The government supports the trial court's determination that "there [was] probable cause to believe [that Thompson had] just bought drugs [on January 31, 1996 in the 600 block of Columbia Road, N.W.]. In addition, the government argues, alternatively, that the officers had "sufficient reasonable articulable suspicion to stop the vehicle driven by . . . Thompson" based on the information relayed by Officer Goodwin, and that "[a]fter stopping the vehicle, the reasonable articulable ...