Defendant contends that the Court of Appeals erred (1) in upholding the trial court’s refusal to dismiss the charges against him on the ground that his Sixth Amendment right to a speedy trial had been violated, and (2) in upholding the trial court’s refusal to dismiss the charges on the ground that he was not brought to trial within eight months after a detainer was filed against him in violation of G.S. 15-10.2(a). These contentions constitute his only assignments of error. We shall discuss them in the order listed.
*140 [1] The right of every person formally accused of crime to a speedy and impartial trial is secured by the fundamental law of this State, State v. Hollars, 266 N.C. 45, 145 S.E. 2d 309 (1965), and guaranteed by the Sixth Amendment to the federal constitution, made applicable to the State by the Fourteenth Amendment. Klopfer v. North Carolina, 386 U.S. 213, 18 L.Ed. 2d 1, 87 S.Ct. 988 (1967). Prisoners confined for unrelated crimes are entitled to the benefits of this constitutional guaranty. State v. Johnson, 275 N.C. 264, 167 S.E. 2d 274 (1969).
[2] The right to a speedy trial is different from other constitutional rights in that, among other things, deprivation of a speedy trial does not per se prejudice the ability of the accused to defend himself; it is impossible to determine precisely when the right has been denied; it cannot be said precisely how long a delay is too long; there is no fixed point when the accused is put to a choice of either exercising or waiving his right to a speedy trial; and dismissal of the charges is the only possible remedy for denial of the right to a speedy trial. Barker v. Wingo, 407 U.S. 514, 33 L.Ed. 2d 101, 92 S.Ct. 2182 (1972).
[3] So, unless a fixed time limit is prescribed by statute, a claim that a speedy trial has been denied must be subjected to a balancing test in which the court weighs the conduct of both the prosecution and the defendant. The main factors which the court must weigh in determining whether an accused has been deprived of a speedy trial are (1) the length of the delay, (2) the cause of the delay, (3) waiver by the defendant, and (4) prejudice to the defendant. Barker v. Wingo, supra; State v. Wright, 290 N.C. 45, 224 S.E. 2d 624 (1976); State v. Brown, 282 N.C. 117, 191 S.E. 2d 659 (1972); State v. Johnson, supra. No single factor is regarded as either a necessary or sufficient condition to the finding of a deprivation of the right to a speedy trial. “Rather, they are related factors and must be considered together with such other circumstances as may be relevant. In sum, these factors have no talismanic qualities; courts must still engage in a difficult and sensitive balancing process. But, because we are dealing with a fundamental right of the accused, this process must be carried out with full recognition that the accused’s interest in a speedy trial is specifically affirmed in the Constitution.” Barker v. Wingo, supra. See Note, The Right to a Speedy Trial, 20 Stan. L. Rev. 476, 478, n. 15 (1968), for a slightly different approach.
*141Thus the circumstances of each particular case must determine whether a speedy trial has been afforded or denied, and the burden is on an accused who asserts denial of a speedy trial to show that the delay was due to the neglect or wilfulness of the prosecution. State v. Johnson, supra. An accused who has caused or acquiesced in the delay will not be allowed to use it as a vehicle in which to escape justice. Barker v. Wingo, supra; State v. Wright, supra; State v. Hollars, 266 N.C. 45, 145 S.E. 2d 309 (1965); State v. Lowry, 263 N.C. 536, 139 S.E. 2d 870, appeal dismissed 382 U.S. 22, 15 L.Ed. 2d 16, 86 S.Ct. 227 (1965).
[4] With these principles in mind we now weigh the four balancing factors in light of the evidence in this case.
The length of delay between defendant’s arrest and trial, almost twenty-two months, is unusual. Of course some delay is permissible in any case because minimal delays are inherent in every trial. “The possibility of unavoidable delay is inherent in every criminal action. The constitutional guarantee does not outlaw good-faith delays which are reasonably necessary for the State to prepare and present its case. . . . Neither a defendant nor the State can be protected from prejudice which is an incident of ordinary or reasonably necessary delay. The proscription is against purposeful or oppressive delays and those which the prosecution could have avoided by reasonable effort. Pollard v. United States, 352 U.S. 354, 1 L.Ed. 2d 393, 77 S.Ct. 481 (1957).” State v. Johnson, 275 N.C. at 273, 167 S.E. 2d at 280. Since “we do not determine the right to a speedy trial by the calendar alone,” State v. Wright, supra, we must consider the length of the delay in relation to the three remaining factors. Barker v. Wingo, supra.
The second factor, the reason for the delay of twenty-two months, is a mixed bag. The grand jury returned the bill of indictment on 10 February 1975 and the case was set for trial on 2 June 1975 but continued on motion of the State for reasons not disclosed. Nothing in the record suggests any purposeful or oppressive delay to this point. Rather, defendant’s silence during this period supports our conclusion that he acquiesced in the delay prior to 2 June 1975. However, defense counsel’s uncon-tradicted affidavit tends to show that failure to bring defendant to trial during the next ten months — from June 1975 to April 1976 —was due to the wilful neglect of the prosecution and could *142have been avoided by reasonable effort. Goaded by Judge McKin-non’s order, the prosecution calendared the case for trial on 12 April 1976. Failure to try it at that time is chargeable, in part if not wholly, to defense counsel’s unavailability. See Judge McLelland’s order and defense counsel’s second affidavit. Thereafter, the case was calendared and tried at the 9 August 1976 Session. Nothing in the record will support a finding of purposeful delay by the prosecution during the period from 12 April to 9 August. We must therefore determine whether countervailing factors outweigh the prosecution’s purposeful, unexplained delay during the ten months from June 1975 to April 1976 in bringing defendant to trial.
We first note that there are no counterbalancing circumstances arising from waiver by defendant. Nothing in the record suggests waiver during the period of ten months from June 1975 to April 1976. To the contrary, defense counsel’s affidavit asserts defendant requested a trial date eight or nine times during that period. The record contains no denial of those allegations. These facts are “entitled to strong evidentiary weight in determining whether defendant is being deprived of the right.” Barker v. Wingo, supra.
The only counterbalancing factor is the fourth: prejudice to defendant was minimal. Defendant’s claim that four of his witnesses became unavailable by reason of the delay is not supported by the record. Edmond Lee Gibson, Charles Daniel Goodwin and Mary Virginia Justice Watson were present at the trial on 9 August 1976 and testified for the State. Anna Wright was absent. We note that in his 22 January 1976 motion to dismiss, defendant did not list Anna Wright as a witness material to his defense. Her name was first included in his February 1976 motions. At the hearing on his motion to dismiss before Judge McLelland, defendant offered evidence tending to show that Anna Wright told Attorney Wade Smith, who originally represented defendant, that she was living with defendant on the day of the shooting; that when Frankie Lee returned to defendant’s apartment, “the word was out” that he had a gun; that defendant ordered Lee to leave his apartment by the count of ten and told her to start counting; that while she was counting, Lee “stuck his hands up in his coat” and defendant shot him.
*143Detective Turnage testified he talked with Anna Wright on 21 October 1974, nine days after the killing, and she stated she was counting as directed by defendant, reached the count of eight or nine, and defendant shot Lee; that defendant then threw the gun on the couch and left; that she never mentioned seeing Lee “stick his hand up in a coat as if to get a gun.” Officer Turnage further testified that he went to the scene of the killing immediately after it occurred and found the victim lying on his face in a pool of blood; that Lee did not have a coat on his person at that time and there was no coat in the immediate vicinity of the body. Moreover, Dr. Gordon LeGrand testified that he performed an autopsy on the body of James Franklin Lee on the morning of 13 October 1974 at which time the corpse was “wearing a red turtle neck sweater and tan plaid pants. . . .”
Although credibility and weight of testimony is a matter for the jury, in light of all the evidence it is highly improbable that the testimony of Anna Wright, had she been present, would have affected the result. Yet her testimony, whether true or false, would have required the trial court to submit the issue of self-defense.
[5] So it comes to this: Does the prosecution’s wilful delay for ten months in bringing defendant to trial outweigh minimal prejudice to defendant occasioned by such delay? On the facts and circumstances revealed by this record the answer is yes. Barring circumstances which justify delay, a defendant desiring a speedy trial is constitutionally entitled to it within a reasonable time. Where, as here, defendant carries the burden of proof by offering evidence which tends to show prima facie that the delay is due to the wilful neglect of the prosecution, the State should offer evidence fully explaining the reasons for the delay and sufficient to rebut the prima facie showing or risk dismissal. The record before us contains no evidence designed to explain or justify the ten-month delay from 2 June 1975 to 12 April 1976. Such indifference to the dictates of the law leaves appellate courts with few options. We hold defendant’s first assignment of error is meritorious and must therefore be sustained.
[6] The other assignment argued in defendant’s brief has no merit. G.S. 15-10.2(a) provides in pertinent part that when a detainer requiring a prisoner to answer a criminal charge pending against him in the courts of this State is filed against any *144prisoner serving a sentence in this State, such prisoner “shall be brought to trial within eight months after he shall have caused to be sent to the district attorney of the court in which said criminal charge is pending, by registered mail, written notice of his place of confinement and request for a final disposition of the criminal charge against him; . . Here, defendant admits that he never sent to the district attorney a notice and request for trial “by registered mail” as required by the statute. We hold that he cannot claim the benefits afforded by the statute without complying with its terms. This accords with prior decisions in State v. Wright, 290 N.C. 45, 224 S.E. 2d 624 (1976), and State v. White, 270 N.C. 78, 153 S.E. 2d 774 (1967).
For the reasons stated we hold that the Court of Appeals erred in sustaining the action of the trial court denying defendant’s motion to dismiss for lack of a speedy trial. The decision of the Court of Appeals is therefore reversed and the case remanded to it for further remand to the Superior Court of Wake County for dismissal of the charges in accordance with this opinion.
Reversed and remanded.