Thus, the issue is whether the jury's ultimate conclusion in this case — under the particular instructions given — constituted a reasonable inference from all the evidence or amounted to an improper, and hence reversible, speculation without evidentiary foundation. This court, in Wishop v. United States, 531 A.2d 1005 (D.C. 1987), stated with respect to the evidence required to prove that a proscribed substance is usable: Edelin [v. United States, 227 A.2d 395 (D.C. 1967)] holds only that if the quantity of a drug is too small to be capable of quantitative analysis, there must be "additional proof of its usability as a narcotic" in order to sustain a conviction.

This burden is not onerous: "'[T]he fact that a drug is measurable — i.e., capable of quantitative analysis — will usually suffice to prove it is usable.'" Judge v. United States, 599 A.2d 417, 419-20 (D.C. 1991) (quoting Wishop v. United States, 531 A.2d 1005, 1008 (D.C. 1987)). In previous cases, this court has found the government's case sufficient, with respect to its burden of proving usable amount, when the government has introduced the following evidence: (1) the total weight of the substance the defendant distributed, (2) the percentage of the total weight consisting of the active drug ingredient, and (3) expert testimony that, based on the total weight and the percentage of active ingredient, the defendant distributed a usable amount.

Thereafter, the number of felony drug trafficking indictments in Superior Court increased from none in 1981 to over 5700 by 1987. The first case involving a felony drug trafficking prosecution, which addressed the issue of the quantity of a controlled substance necessary for conviction, was Wishop v. United States, 531 A.2d 1005 (D.C. 1987), which we will examine at length later in this opinion. In the meantime, however, two DC-CSA misdemeanor possession prosecutions raising the issue had come before the court.

Proof of narcotic effect is only required where a minute amount of a controlled substance that "cannot be sold, . . . administered[,] or dispensed" has been recovered. Wishop v. United States, 531 A.2d 1005, 1007 (D.C. 1987) (quoting Edelin v. United States, 227 A.2d 395, 398-99 (D.C. 1967)). See also Judge, supra, 599 A.2d at 420 (distinguishing Singley v. United States, 533 A.2d 245, 247 (D.C. 1987)).

" The cases following Edelin hold, in substance, that proof of a usable amount can be established in different ways. Gray v. United States, 600 A.2d 367, 369 (D.C. 1991). We have held, for example, that evidence of usability can ordinarily be established by showing that the quantity of the substance is measurable. Gray, supra, 600 A.2d at 369 (citing Wishop v. United States, 531 A.2d 1005, 1008 (1987) (holding that the fact that the drug is measurable is persuasive that it is also usable)). We have also held that usability can be established through opinion evidence, ordinarily from experienced police officers qualified as expert witnesses on the subject, that the controlled substance is a usable amount.

In other decisions as well, we have narrowly construed Edelin's requirement of proof of utility as a narcotic. Thus in Wishop v. United States, 531 A.2d 1005 (D.C. 1987), we stated: " Edelin holds only that if the quantity of a drug is too small to be capable of quantitative analysis, there must be 'additional proof of its usability as a narcotic' in order to sustain a conviction." Id. at 1008 (emphasis added) (quoting Edelin, 227 A.2d at 399).

These were sufficient factual bases for Officer Sinclair's expert opinion that the cocaine seized was a usable amount. See Wishop v. United States, 531 A.2d 1005, 1008-1009 (D.C. 1987). Appellant also contends that Officer Sinclair's definition of "usable amount" reflected an erroneous interpretation of the law — a contention which, if true, would call into question his expert opinion that the cocaine satisfied the legal requirement of usability.

The government's expert testified that the cocaine was a usable amount to be ingested in the normal fashion and that "this amount would go for about $20 on the street." In Wishop v. United States, 531 A.2d 1005 (D.C. 1987), this court stated that "the fact that a drug is measurable — i.e., capable of quantitative analysis — will usually suffice to prove it is usable." 531 A.2d at 1008.

Thorne also claims that the government engaged in misconduct in relation to Count 3 because the chemical analysis by the Drug Enforcement Administration of the material which he allegedly sold to Wood on November 6, 1983 had revealed that it contained only traces of heroin, rather than a usable amount. See Wishop v. United States, 531 A.2d 1005, 1009 (D.C. 1987). Thorne's theory is that the government improperly obtained an indictment and used it to prejudice the jury against him in obtaining his conviction on the preludin count. The existence of a usable amount may, however, be established by circumstantial evidence.

We review the jury instructional issue for plain error, being mindful that: "`It is the rare case in which an improper instruction will justify reversal of a criminal conviction when no objection has been made in the trial court.'" Wishop v. United States, 531 A.2d 1005, 1008 (D.C. 1987) (quoting Henderson v. Kibbe, 431 U.S. 145, 154 (1977) (footnote omitted)). In examining the alleged error, we review the instructions in their entirety.