
325 S.E.2d 518 (1985)
STATE of North Carolina
v.
Rufus NEWKIRK, Jr.
No. 844SC329.
Court of Appeals of North Carolina.
February 19, 1985.
*520 Atty. Gen. Rufus L. Edmisten by Asst. Atty. Gen. Douglas A. Johnston, Raleigh, for the State.
Appellate Defender Adam Stein by James R. Glover, Raleigh, for defendant.
WELLS, Judge.
Defendant brings forth three assignments of error, contending that the trial court erred in (1) failing to require the state to account for the whereabouts of its confidential informant, Earl Gray; (2) failing to adequately instruct the jury so as to require that the state prove both sale and delivery counts as to Officer Smith; and (3) entering judgment for two counts of possession of the same controlled substance. We find no prejudicial error.
In his first assignment of error, defendant contends that the trial court improperly refused to require the state to use reasonable efforts to produce Earl Gray at trial. Essentially, defendant argues that he was entitled to an order from the trial court directing the state to attempt to locate the confidential informant, or to make a showing that his absence occurred in spite of reasonable efforts to ensure his presence at trial.
It is well established that the state is privileged to withhold from a defendant the identity of a confidential informant, with certain exceptions. The test applied, when disclosure of an informant's identity is requested, is set forth in Roviaro v. United States, 353 U.S. 53, 77 S.Ct. 623, 1 L.Ed.2d 639 (1957). The government, to promote disclosure of crimes, may withhold a confidential informant's identity except when disclosure of a communication will not reveal the name of the informer, or when the informer's identity has already been disclosed.
A further limitation on the applicability of the privilege arises from the fundamental requirements of fairness. Where the disclosure of an informer's identity, or of the contents of his communication, is relevant and helpful to the defense of an accused, or is essential to a fair determination of a cause, the privilege must give way. In these situations the trial court may require disclosure and, if the Government withholds the information, dismiss the action.
Id.; see also State v. Gilchrist, 71 N.C. App. 180, 321 S.E.2d 445 (1984). Once defendant has made a "plausible" showing of the materiality of the informer's testimony, United States v. Valenzuela-Bernal, 458 U.S. 858, 102 S.Ct. 3440, 73 L.Ed.2d 1193 (1982), State v. Grainger, 60 N.C.App. 188, 298 S.E.2d 203 (1982), disc. rev. denied, 307 N.C. 579, 299 S.E.2d 648 (1983), the trial court must balance the public's interest with defendant's right to present his case "taking into consideration the crime charged, the possible defenses, the possible significance of the informer's testimony, and other relevant factors." Roviaro v. United States, supra; see also State v. Cameron, 283 N.C. 191, 195 S.E.2d 481 (1973). Two factors weighing in favor of disclosure are (1) the informer was an actual participant in the crime compared to a mere informant, e.g., Roviaro v. United States, supra; State v. Ketchie, 286 N.C. 387, 211 S.E.2d 207 (1975), and (2) the state's evidence and defendant's evidence contradict on material facts that the informant could clarify, McLawhorn v. State of North Carolina, 484 F.2d 1 (4th Cir.1973); State v. Orr, 28 N.C.App. 317, 220 S.E.2d 848 (1976). Several factors vitiating against disclosure are whether the defendant admits culpability, offers no defense on the merits, or the evidence independent of *521 the informer's testimony establishes the accused's guilt. State v. Cameron, supra.
Upon cross examination of Officer Smith, defendant, for the first time, requested the identity and current whereabouts of the confidential informer briefly mentioned in Officer Smith's direct examination. The state initially objected to disclosure but promptly withdrew the objection. Officer Smith identified the informer as Earl Gray, but denied any knowledge of his present whereabouts. Following cross examination, defendant moved for the trial court to compel the state to produce Gray's current address, telephone number, or contact him in order "to see if he's [sic] any exculpatory evidence that we might use." Defendant justified this request based on Officer Smith's testimony that Gray was a witness to the occurrences inside the restaurant and remained in defendant's presence while Officer Smith and Shaheed consummated the alleged drug sale outside.
The trial court extensively questioned Lieutenant Paul Buchanan, Supervisor of the Special Operations Division in charge of the undercover operation, as to Gray's present whereabouts. Buchanan informed the trial court that Gray was a professional confidential informant who moved about the state and that he had attempted to locate Gray for two months without success, even making inquiries of the State Bureau of Investigation, who had employed Gray on occasion and was Gray's last known employer. The trial court denied defendant's motion indicating if Gray had been in Onslow County that he would compel his production, but as his testimony would not appear to be helpful to defendant, attempting to locate him might jeopardize any undercover operation he was presently involved in.
We hold that the trial court's denial of defendant's motion to compel the state to locate Gray was proper. Assuming for the purpose of this appeal that Gray was a participant in the alleged transactions and that his testimony could have helped clarify Officer Smith's testimony, the state cannot be compelled to produce a witness it cannot, in good faith, locate after a reasonable search. In State v. Brockenborough, 45 N.C.App. 121, 262 S.E.2d 330 (1980), the court affirmed the trial court's denial of the defendant's request for the state to produce an informer stating:
Prior to arraignment and trial, the court declared ... [the informant] a material witness and ordered the State to furnish defendant with the best information available to the district attorney and local law enforcement officers as to ... [the informant's] whereabouts. It was further ordered that if an address for ... [the informant] was found, the State was to inform the court and defendant. We hold this was all the State was required to do.
In the case before us, it clearly appears that the state made a good faith attempt to locate the informer but was unable to do so. Unlike Brockenborough, the trial court did not order the state to provide Gray's whereabouts if he was located, but this was the result of defendant's motion being made during the first day of a two day trial rather than at arraignment. Under the facts of this case, we find that the state's good faith effort to locate the confidential informant was all that was required. This assignment is overruled.
In defendant's second assignment of error he contends that the trial court improperly instructed the jury on sale and delivery of a controlled substance. He argues that the following portion of the jury charge permitted conviction if defendant delivered a controlled substance to Shaheed without knowing that Shaheed would sell and deliver the controlled substance.
Now, handing a phenmetrazine tablet to Akhtab Shaheed for exchange of twenty dollars from J.P. Smith that's, that handing being done by the defendant would be a sale and delivery of a controlled substance.
It is axiomatic in this state that the trial court's jury charge must be construed contextually as a whole and that isolated errors are not necessarily prejudicial. State v. Bailey, 280 N.C. 264, 185 S.E.2d 683, *522 cert. denied, 409 U.S. 948, 93 S.Ct. 293, 34 L.Ed.2d 218 (1972). Placing the contested portion of the jury charge in context, the trial court instructed:
[T]o find the defendant guilty of selling and delivering phenmetrazine, a controlled substance, the State must prove beyond a reasonable doubt that the defendant knowingly sold and delivered phenmetrazine to J.P. Smith.

Now, handing a phenmetrazine tablet to Akhtab Shaheed for exchange of twenty dollars from J.P. Smith that's, that handing being done by the defendant would be a sale and delivery of a controlled substance. Now, I instruction you for a person to be guilty of a crime, it is not necessary that he himself do all of the acts necessary to constitute the crime. If two or more persons acting together with a common purpose to commit sale and delivery of phenmetrazine, each of them is held responsible for the acts of the others done in the commission of selling phenmetrazine.

So, I charge if you find from the evidence that ... Rufus Newkirk, Jr. acting either by himself or acting together with Akhtab Shaheed knowingly handed a phenmetrazine tablet to Akhtab Shaheed for exchange of twenty dollars from J.P. Smith, it would be your duty to return a verdict of guilty as charged. [Emphasis added].
Viewing the trial court's instruction contextually, the trial court properly instructed that defendant, to be convicted, must have knowingly given a controlled substance to Shaheed for the purpose of selling and delivering it to Officer Smith. This assignment is overruled.
In defendant's final assignment of error he contends that the trial court erred by entering judgment for two convictions of possession of the same controlled substance, contending that he was twice put in jeopardy for the same offense. "For the plea of former jeopardy to be good, the plea must be grounded on the `same offense' both in law and in fact." State v. Lewis, 32 N.C.App. 298, 231 S.E.2d 693 (1977) (quoting State v. Cameron, supra). Shaheed's and Officer Smith's testimony clearly establishes that Shaheed obtained a different tablet of the same controlled substance on two separate days from defendant. Defendant's possession, therefore, was different both in law and in fact. This assignment of error is overruled.
The record before us reflects that defendant received a fair trial in which we find
No error.
ARNOLD and COZORT, JJ., concur.
