
545 P.2d 604 (1976)
STATE of Oregon, Respondent,
v.
Orlando Arthur VANCE, Appellant.
Court of Appeals of Oregon.
February 3, 1976.
Robert C. Cannon, Deputy Public Defender, Salem, argued the cause for appellant. With him on the brief was Gary D. Babcock, Public Defender, Salem.
James A. Hill, Asst. Atty. Gen., Salem, argued the cause for respondent. With him on the brief were Lee Johnson, Atty. Gen., and W. Michael Gillette, Sol. Gen., Salem.
Before SCHWAB, C.J., and LANGTRY and FORT, JJ.
SCHWAB, Chief Judge.
Upon trial by jury, defendant was convicted of criminal activity in drugs by furnishing heroin, ORS 167.207. Defendant contends that the trial court erred (1) in denying his motion to dismiss for pre-indictment delay, and (2) in allowing the *605 heroin to be introduced into evidence without a sufficient chain of custody being established.
Defendant was indicted on January 30, 1975. On September 20, 1974, a special agent of the Federal Drug Enforcement Administration purchased heroin from defendant in northeast Portland after being led to the location by a named informant. There were several policemen present, including Portland City Police Officer Kanzler, who observed the meeting of the special agent, the informant and defendant. Defendant testified that he could not remember where he was or what he was doing on September 20.
The special agent did not stay in contact with the informant. Although not permanently employed, this informant had acted for Officer Kanzler 20 or more times and was paid on six or seven occasions. Kanzler's last contact with informant was in December 1974 or January 1975. At that time the informant indicated that someone had "shot up his car" and that defendant and his sister had put out a "contract" on the informant, the special agent and Kanzler. Although the officer did not urge the informant to stay out of sight, the informant told the officer he was going to be very cautious when he came to Portland.
The circuit court would have been required to grant defendant's motion to dismiss the indictment only
"`* * * if it were shown at trial that the pre-indictment delay in this case caused substantial prejudice to [defendant's] rights to a fair trial and that the delay was an intentional device to gain tactical advantage over the accused. * * *'" State v. Serrell, 265 Or. 216, 219-20, 507 P.2d 1405, 1406 (1973) (quoting from United States v. Marion, 404 U.S. 307, 324, 92 S.Ct. 455, 30 L.Ed.2d 468 (1971)).
The accused has the burden of proving prejudice to his right to due process. State v. Serrell, supra, 265 Or. at 220, 507 P.2d 1405; accord, State v. Heyer, 16 Or. App. 22, 25, 517 P.2d 314 (1973), Sup. Ct. review denied (1974); State v. Gunn, 16 Or. App. 26, 29, 517 P.2d 316 (1973), Sup. Ct. review denied (1974); and State v. Brown, Or. App., 75 Adv.Sh. 3571, 541 P.2d 491 (1975).
Defendant argues that the pre-indictment delay caused him substantial prejudice by preventing him from presenting at trial an essential eyewitness, the informant.[1] Defendant does not contend that the delay was "an intentional device to gain tactical advantage" over him. The court, in fact, found that the delay was "attributable to the use of undercover officers." See generally, Amsterdam, Speedy Criminal Trial: Rights and Remedies, 27 Stan.L.Rev. 525, 527 (1975).
Defendant's inability to locate witnesses may well be a factor in deciding whether pre-indictment delay caused substantial prejudice to an accused. Here, defendant claims that the informant was crucial to a defense of misidentification. Following the drug transaction the special federal agent filed a report in which he described seller as having "noticeable gold caps on his front teeth." At the time of trial defendant did not have any gold caps on his teeth. He testified that he had not been to the dentist for six years.
The description discrepancy is not as significant as it might seem in light of strong evidence identifying defendant as the person who sold heroin to the special agent. The special agent identified defendant correctly in Portland Police Department, Portland Police Bureau, Oregon *606 State Police Bureau and FBI mug shots. The special agent also made a courtroom identification of defendant. Furthermore, Officer Kanzler testified that he had known defendant since 1968 and that he recognized defendant as the person he saw meet the special agent and the informant at the time of the drug transaction. We find that defendant's failure to locate and produce the informant did not prejudice him.
Defendant contends that the prosecution had a duty to keep the informant available so that he could be called as a defense witness because his testimony was essential to the defense. In the court below, however, defendant did not make a motion seeking to require the state to produce the informant. See, State v. Cortman, 251 Or. 566, 574, 446 P.2d 681 (1968), cert. denied 394 U.S. 951, 89 S.Ct. 1294, 22 L.Ed.2d 487 (1969). Therefore, we do not consider this on appeal.
Defendant also urges us to find there is a fatal gap in the evidence chain. The forensic chemist who tested the heroin in San Francisco testified that he did not personally take receipt of the evidence at the post office, but got it from the custodian who picks up the registered mail. The custodian did not testify.
The Oregon Supreme Court addressed this issue in State v. Anderson, 242 Or. 368, 409 P.2d 681 (1966). The court stated:
"It may be conceded that, ordinarily, when an object is taken from the defendant for the purpose of testing and passes through the hands of several persons a foundation for its admission into evidence must be laid by the testimony of each person who had possession or custody of the article: 2 Wharton's Criminal Evidence (12th ed.) 586, § 665. But this is not an inexorable rule of law and the ultimate question always is whether the proof shows with reasonable certainty that the article offered is the identical article taken from the accused. That question is addressed in the first instance to the sound discretion of the trial judge.
"* * *
"`* * * Factors to be considered in making this determination include the nature of the article, the circumstances surrounding the preservation and custody of it, and the likelihood of intermeddlers tampering with it. If upon the consideration of such factors the trial judge is satisfied that in reasonable probability the article has not been changed in important respects, he may permit its introduction in evidence.' * * *"
It was not error for the trial court to find that the heroin was admissible in this case. Defendant's argument concerning the weak link goes to the weight of the evidence and could have been considered by the jury as the trier of fact. Cf., State v. Shirley, 1 Or. App. 635, 644, 465 P.2d 743 (1970).
Affirmed.
NOTES
[1]  Defendant recognizes that it is settled that he "does not carry his burden by claiming he does not remember where he was on the day the crime was alleged to have been committed." State v. Serrell, 265 Or. 216, 220, 507 P.2d 1405, 1407 (1973); State v. Heyer, 16 Or. App. 22, 25, 517 P.2d 314 (1973), Sup. Ct. review denied (1974); State v. Gunn, 16 Or. App. 26, 29, 517 P.2d 316 (1973), Sup. Ct. review denied (1974); State v. Brown, Or. App., 75 Adv.Sh. 3571, 3573, 541 P.2d 491 (1975).
