In State v. Sanchez, 143 N.J. 273, 670 A.2d 535 (1996), the Court noted that when there is more than one defendant, and "'much of the same evidence is needed to prosecute each defendant, a joint trial is preferable.'" State v. Sanchez, supra, 143 N.J. at 281, 670 A.2d 535, (quoting State v. Brown, 118 N.J. 595, 605, 573 A.2d 886 (1990)). However, notwithstanding considerations of judicial efficiency which may favor a joint trial, "the interest in judicial economy cannot override a defendant's right to a fair trial." Id. at 282, 670 A.2d 535. Thus, R. 3:15-2(b) provides relief from what would be a prejudicial joinder and "as a general matter ... 'the decision whether to grant severance rests within the trial court's sound discretion.'" Id. at 282-83, 670 A.2d 535. The fact that a co-defendant may provide exculpatory. testimony if two defendants are tried separately, may provide a basis for severance. Thus,evaluating severance motions that are based on the need for a co-defendant's testimony requires a balancing of the State's interest in the economy of a joint trial and a criminal defendant's interest in presenting exculpatory evidence to the trier of fact. Jointly indicted defendants generally should be tried together to avoid unnecessary, duplicative litigation. "Nevertheless, a single joint trial, however desirable from the point of view of efficient and expeditious criminal adjudication, may not be had at the expense of a defendant's right to a fundamentally fair trial." Id. at 290, 670 A.2d 535. In weighing such a request and evaluating the competing interests, the key considerations are "the exculpatory nature of the proffered testimony; and ... a showing that the testimony would be forthcoming in a separate trial." Id. at 286-87, 670 A.2d 535. The focus should be "on the substance and quality of the proffered testimony," and the court should "distinguish between credible, substantially exculpatory testimony and testimony that is insignificant, subject to damaging impeachment, or unduly vague conclusory, or cumulative." Id. at 291, 670 A.2d 535. Where it is shown that the co-defendant will provide "credible" and "substantially exculpatory" testimony at a separate trial (even if the codefendant conditions that willingness on his being tried first), the trial court should grant a severance. Thus the Court summarized its conclusions: We hold that the trial court should sever a joint trial if the court is reasonably certain that: (1) the defendant will call his co-defendant as a witness in a separate trial; (2) the co-defendant, although unwilling to testify at a joint trial, will testify at a separate trial either prior or subsequent to his own trial; (3) the codefendant's proffered testimony will be credible and substantially exculpatory. . . . A co-defendant's conditional offer to testify should carefully be assessed by a trial court in determining whether the risk of perjury outweighs the likelihood that the proffered testimony is trustworthy. But the focus of the severance analysis should be on the exculpatory value of the proffered testimony, and not on whether the defendant requests to be tried before his codefendant.Id. at 293, 670 A.2d 535. In Sanchez, the Court concluded that the defendant had not made the kind of showing which required the trial court to grant the requested severance. The co-defendant had been equivocal as to whether he would testify for the defendant even with a severance. His brief description of what he would say if he testified was not clearly exculpatory of the defendant, and actually suggested that the defendant was implicated in the crime. Because the defendant "failed to show that substantially exculpatory testimony would have been forthcoming had his severance motion been granted," the Court found no prejudice and thus no error in denying the requested severance. Id. at 295, 670 A.2d 535.