Defendant argues four assignments of error in his brief. Our review of the factual circumstances of this record and the law applicable thereto does not, however, disclose prejudicial error requiring a new trial. We therefore affirm defendant’s conviction for first degree murder.
 Defendant first contends that the trial court erred in failing to grant his motion for severance from a joint murder trial with Abrams. We disagree.
To begin with, we hold that the cases of defendant and Abrams were properly joined for trial pursuant to G.S. 15A-926(b)(2) since both were charged with accountability for the same offense. That being so, it is clear that the disposition of defendant’s subsequent motion for a separate trial was a matter governed by the judge’s sound discretion. State v. Allen, 301 N.C. 489, 272 S.E. 2d 116 (1980); State v. Slade, 291 N.C. 275, 229 S.E. 2d 921 (1976). Our Court has held repeatedly that the ruling upon a motion for severance shall not be disturbed on appeal unless defendant demonstrates an abuse of judicial discretion which effectively deprived him of a fair trial. See, e.g., State v. Porter & Ross, 303 N.C. 680, 281 S.E. 2d 377 (1981); State v. Crews, 296 N.C. 607, 252 S.E. 2d 745 (1979); State v. Smith, 291 N.C. 505, 231 S.E. 2d 663 (1977); see G.S. 15A-927(c)(2). We find no such abuse here.
It is true that the testimony of Abrams and defendant was conflicting upon material facts, and their defenses were admittedly antagonistic. However, Abrams was subjected to vigorous cross-examination by defendant’s counsel, and, more importantly, the State offered other sufficient evidence of defendant’s guilt of the crime (in particular, the testimony of Toby Locke). It is also plain that Abrams could have testified about the very same in*148criminating matters at defendant’s separate trial.1 Under these circumstances, we cannot say, as a matter of law, that the antagonistic defenses of the co-defendants converted this joint trial into an impermissible evidentiary contest or combative spectacle which prevented the jury from rendering a fair adjudication of defendant’s individual guilt. See State v. Nelson, 298 N.C. 573, 260 S.E. 2d 629 (1979), cert. denied, 446 U.S. 929, 100 S.Ct. 1867, 64 L.Ed. 2d 282 (1980); State v. Cook, 48 N.C. App. 685, 269 S.E. 2d 743, petition for discretionary review denied, 301 N.C. 528, 273 S.E. 2d 456 (1980). As there is an insufficient basis for finding that the judge abused his discretion in denying severance, the assignment of error is overruled.
 Defendant additionally argues that the trial court should have suppressed the State’s evidence of Toby Locke’s written statement because he was not afforded, as requested, an opportunity for pre-trial discovery of its contents pursuant to G.S. 15A-903(b) and (d). Defendant’s position is untenable. We agree that G.S. 15A-903(b) and (d) generally require the State to disclose the statements of a co-defendant and documents or tangible objects which are material to the preparation of the defense. However, neither of these discovery provisions applies in the instant case. First, the State did not have to reveal the statement’s contents under G.S. 15A-903(b)(2) because Locke, although charged with the same murder, was not a co-defendant being jointly tried with defendant. State v. Moore, 301 N.C. 262, 271 S.E. 2d 242 (1980). Second, the State had no statutory duty to divulge the prior recorded statement of Locke under G.S. 15A-903(d) because Locke was testifying for the prosecution (under an offer of immunity), and the State could properly resist discovery of its witness’s statement under G.S. 15A-904(a). State v. Abernathy, 295 N.C. 147, 244 S.E. 2d 373 (1978); State v. Hardy, 293 N.C. 105, 235 S.E. 2d 828 (1977). In sum, we hold that Locke’s statement was not discoverable by defendant under G.S. 15A-903; consequently, the statement was correctly admitted into evidence to corroborate Locke’s in-court testimony.
*149Defendant’s next assignment of error states that “[t]he trial judge abused his discretion by denying defendant’s numerous motions for mistrial due to improper conduct on the part of the district attorney.” (Emphasis added.) The record shows that defendant specifically moved for a mistrial only twice, yet this assignment attempts to incorporate, for our consideration, seventeen exceptions taken by defendant at various times throughout the trial. Only two of those exceptions, nos. 3 and 22, were directed to the denial of defendant’s motions for a mistrial. It is, therefore, appropriate that we limit our review of this assignment of error to the specific matters challenged by exceptions 3 and 22. See North Carolina Rules of Appellate Procedure, Rule 10(a) (“no exception . . . which is not made the basis of an assignment of error may be considered on appeal”); Rule 10(c) (“[e]ach assignment of error . . . shall, so far as practicable, be confined to a single issue of law”); Rule 28(b)(3) (content of appellant’s brief: “[ijmmediately following each question shall be a reference to . . . exceptions pertinent to the question”).
 With regard to exception no. 3, defendant essentially contends that the trial court should have ordered a mistrial upon the ground that a defense witness had been improperly questioned, on the night before trial, by two detectives of the Jacksonville Police Department at the behest of the district attorney. We disagree. The trial court conducted a prompt and thorough voir dire hearing investigating defendant’s allegation. The two detectives involved and the witness interviewed by them were subjected to full examination by both the defense and prosecution. At the conclusion of its investigation, the court entered the following order:
From the evidence offered on the voir dire the Court makes the following findings of fact: Ronnie Guthrie, a witness under subpoena by the defendant, was returned from the Department of Correction to the Onslow County Jail on Tuesday, September 2, and has remained there since that time.
2. At the request of the District Attorney, Detectives Delma Collins and W. T. Whitehead interviewed Guthrie in the Onslow County Jail on the night of Wednesday, September 3.
*150The purpose of the interview was to determine what testimony Guthrie was prepared to give in this case with respect to what one Kevin Lake had said at the time that Guthrie was in the Onslow County Jail with Lock (sic) and the defendant Lake. Guthrie did talk to the officers in the conference room at the Onslow County Jail. The officers did not threaten or intimidate Guthrie. The motion for mistrial is denied.
It is axiomatic that the trial court’s findings entered upon a voir dire hearing are conclusive and binding on appeal if they are supported by competent evidence. See State v. Thompson, 303 N.C. 169, 277 S.E. 2d 431 (1981); State v. Gray, 268 N.C. 69, 150 S.E. 2d 1 (1966), cert. denied, 386 U.S. 911, 87 S.Ct. 860, 17 L.Ed. 2d 784 (1967). It would serve no useful purpose for us to recap the content of the witnesses’ testimony2 heard by the judge. It suffices to say that we have carefully reviewed the pertinent portions of the record and find therein ample competent evidence to sustain the judge’s findings; therefore, it does not affirmatively appear that the judge abused his discretion in denying the motion for a mistrial in this respect.
 With regard to exception no. 22, defendant essentially maintains that he was entitled to the declaration of a mistrial because the district attorney, in his closing argument to the jury, attempted to discredit two defense witnesses by asserting certain facts which were not included in the evidence presented at trial. It is, of course, well established that, although wide latitude is permitted in jury argument, counsel may not transcend the bounds of fundamental fairness and argue extraneous facts or law not properly in evidence. State v. Wright, 304 N.C. 349, 283 S.E. 2d 502 (1981); State v. Lynch, 300 N.C. 534, 268 S.E. 2d 161 (1980). The district attorney committed this very transgression in the instant case. However, the judge immediately sustained defendant’s objection to the challenged argument and plainly instructed the jury to disregard the inappropriate statements in its deliberations. This curative instruction adequately averted any possible prejudice to defendant. State v. Sanders, 303 N.C. 608, 281 S.E. 2d 7 (1981); State v. Covington, 290 N.C. 313, 226 S.E. 2d 629 (1976). *151For this reason, we conclude that the judge did not abuse his discretion in failing to grant a mistrial for the district attorney’s impropriety.
Defendant finally contends that the cumulative effect of various errors at trial, including those we have discussed, resulted in the denial of a fair trial; thus, the trial court erred in denying his motion for appropriate relief. This contention lacks merit and is overruled.
In conclusion, we find no prejudicial error in defendant’s trial, and the judgment of life imprisonment is affirmed.