Jimmy Wayne Mullins and Kimberly Carmela Mullins were charged in a two-count indictment with possession of amphetamines with intent to distribute and possession of less than an ounce of marijuana. Both were found guilty by a jury, and they appeal, alleging that the State failed to prove an adequate chain of custody for the contraband seized from their home and that the trial court erred in denying their motion for a mistrial based upon juror misconduct. Although we find that the State proved an adequate chain of custody, we conclude that a mistrial should have been declared, and we therefore reverse.
1. The Appalachian Drug Task Force executed a search warrant on the home of Jimmy and Kimberly Mullins on January 10, 1997. Agent John Cagle found Jimmy Mullins in the bathroom of the house trying to flush several plastic bags down the toilet. Agent Cagle was able to retrieve these bags and seize the contraband. He initialed the evidence bags and turned them over to Agent Shane Henson at the scene. Henson placed them, along with other items seized from the home, including marijuana, electronic scales, plastic “corner” baggies, a can or jar of Fruit Fresh, and a smoking pipe, into the trunk of his vehicle and locked the trunk. Henson testified that he first placed the evidence in the secured evidence locker at the office of the Appalachian Drug Task Force in Dawson County and that he later carried it personally to the Georgia Bureau of Investigation crime lab in Decatur for testing. At trial, Henson identified State’s Exhibits 1 and 2 as the samples he took from the Mullinses’ home and eventually delivered to the crime lab.
Unaiza Ali, a forensic chemist at the crime lab, testified that she received State’s Exhibit 1 from her supervisor, Mark Burns, on May 26, 1998. The sample had been taken from the lock box by Lonnie Jones, who was then employed at the crime lab as a forensic chemist, and it was analyzed by Jones. Because Jones was no longer employed at the crime lab, the prosecutor requested that the sample be analyzed again. Ali analyzed the sample anew, and she identified it as amphetamine.
Ali testified that when she received the evidence bag, it was not sealed but was stapled shut. She stated that it bore a “unique crime *554lab number” corresponding to the case and she had no concern that the sample might have been mixed up, tampered with, or contaminated.
. In two enumerations, the Mullinses contend the trial court erred in allowing State’s Exhibit 5, the laboratory report, into evidence and in failing to strike Ali’s testimony. They contend the chain of custody was deficient based upon the failure of Jones, the original testing chemist, to testify, even though the laboratory report included his findings; the failure to seal the sample between the two analyses; and the large discrepancy in the report between the weight of the sample as found by Jones and Ali. For several reasons, we do not agree that the chain of custody was materially deficient.
First, when the State wishes to introduce evidence of a fungible nature, its burden is simply to show that the evidence is the same as that seized and that it has not been tampered with or substituted. Scott v. State, 227 Ga. App. 900, 901 (2) (490 SE2d 208) (1997). The State need not rule out every possibility of tampering, but the “circumstances must establish reasonable assurance of the identity of the substance. [Cit.]” Staples v. State, 209 Ga. App. 802, 805 (5) (434 SE2d 757) (1993).
The State’s burden was discharged in this case. The State need not establish a “perfect” chain of custody for evidence within the crime lab itself. Here, as in Scott, the crime lab employee who originally received and analyzed the sample did not testify; here, as there, the technician who testified received the sample from her superiors. Id. at 900 (2). We held that the chain of custody shown was sufficient. The Mullinses offered no evidence of tampering. A discrepancy in weight was shown in Staples. But here, as in Staples, the possibility of complete substitution was rebutted by testimony concerning procedures used to identify and store evidence. Id. at 806 (5).
Second, the fact that the sample was stapled but not sealed goes to the weight of the evidence and not its admissibility. “Where there is only a possibility of tampering, substitution, or misidentification, it is proper to admit the evidence and let what doubt remains go to its weight.” (Citations and punctuation omitted.) Staples, supra.
Third, any issue with regard to the weight discrepancy has been waived, because it was not raised at trial. The same is true of the issue the Mullinses raise on appeal regarding Ali’s receipt of the evidence from outside the crime lab prior to her analysis.1 A party may *555not during trial remain silent concerning what he believes to be an error or injustice and hope to complain later if the verdict is not favorable. See, e.g., Anthony v. State, 236 Ga. App. 257, 258 (1) (511 SE2d 612) (1999). The trial court did not err in admitting the lab report or in allowing the testimony of Ali.
2. The Mullinses’ remaining enumeration concerns an instance of alleged juror misconduct. The record shows that during a court recess, two jurors standing in the hallway were approached by an acquaintance with no connection with this trial. Their conversation was overheard and reported to the trial judge. After the recess, the trial judge took sworn testimony from the three participants in the encounter.
The acquaintance denied talking to the two jurors about anything connected to the trial, and the two jurors swore likewise. The judge, puzzled by the discrepancy between what had been reported to him and this testimony, then questioned defense counsel, who related that several witnesses informed him they heard the acquaintance tell the two jurors that the defendants would not be in court if they were not guilty, and they heard one juror agree.
The trial court requestioned the acquaintance, who reported that if he did make that comment he did not recall it. Upon requestioning, however, the two jurors admitted hearing their acquaintance make the comment related to defense counsel. But they steadfastly denied replying to the comment. The judge inquired of the jurors whether their acquaintance’s comment would in any way affect their ability to decide the case based upon the evidence presented, and both replied that it would not. The defense moved for a mistrial, which was denied.
After the two jurors were returned to the jury room, Kimberly Mullins was sworn and testified that she heard one juror reply to the acquaintance’s remark. She stated that when the acquaintance told the two jurors the defendants would not be in court if they were not guilty, one juror replied, ‘Yeah, I know.” The defense again moved unsuccessfully for a mistrial. When the jurors returned, the trial court admonished them that if they heard anything during the break, they were to disregard what they heard and decide the case solely upon the evidence presented in court.
The trial proceeded without further incident until the close of evidence. Shortly before the charge conference, defense counsel placed in the record that he knew the court had ruled on his motion for mistrial, but that he had requested that the court remove the two jurors involved in the incident. The trial court acceded to this request, finding specifically that the jurors did nothing wrong “but out of an abundance of caution on behalf of your clients to protect the integrity of their trial by jury,” only after the defense agreed to pro*556ceed with just ten jurors.
On appeal, the Mullinses contend that a mistrial should have been declared and that the trial court abused its discretion in failing to do so. We must agree. “When irregular juror conduct is shown, there is a presumption of prejudice to the defendant, and the prosecution carries the burden of establishing beyond a reasonable doubt that no harm occurred.” (Footnote omitted.) Holcomb v. State, 268 Ga. 100, 103 (2) (485 SE2d 192) (1997). To upset a jury verdict, the misconduct must have been “so prejudicial that the verdict is deemed inherently lacking in due process.” (Punctuation and footnote omitted.) Id.
In this case, we find no evidence in the record that the State met its burden of establishing that no harm occurred. This case is unlike those in which we have found that the substance of the extrajudicial communication was established without contradiction and the facts themselves established lack of prejudice to the defendant. See, e.g., Sims v. State, 266 Ga. 417, 419-420 (3) (467 SE2d 574) (1996) (juror statements to each other did not involve extrajudicial information or demonstrate they were deliberating or attempting to persuade each other); Holcomb, supra. Here, testimony regarding whether the juror responded to the acquaintance’s remark was in conflict. The State did not establish whether the two jurors involved discussed the matter with the other jurors; the remaining jurors were not questioned.
We must decide, therefore, whether the incident was so prejudicial that the jury’s verdict was tainted.
The decision whether any unauthorized statement, communicated to the jury either individually or as a group, is so prejudicial as to warrant a mistrial is in the discretion of the trial court. Some of the factors and circumstances to be reviewed in determining whether the trial court abused its discretion in denying the motion for mistrial include the nature of the statement, the other evidence in the case, and the action taken by the court and counsel concerning the impropriety.
(Citations and punctuation omitted.) Cooke v. State, 230 Ga. App. 326, 327 (496 SE2d 337) (1998). The question presented here is a close one, but we conclude that under these particular facts and circumstances, the misconduct was so prejudicial that a mistrial was warranted, and the trial court erred in failing to declare one.
The statement related to the defendants’ guilt or innocence, the ultimate issue for jury resolution. The testimony was in conflict as to whether one of the jurors indicated that he, too, had predetermined the defendants’ guilt. The State did not establish that this view had *557not been transmitted to the rest of the jury. And the very fact that the jurors first denied even hearing the remark placed the defense in the unenviable position of contradicting a sworn statement by the jurors before the jurors reluctantly admitted that the defense allegation was true, even in part. Although the two jurors did not participate in the verdict, we conclude that possible personal resentment on their part after having been contradicted and forced to change their testimony may very well have contributed to the verdict. The defense’s agreement, as a last resort, to proceed with a jury of ten precisely to avoid such contamination does not constitute a waiver of the right to raise this issue on appeal. Under these circumstances, a mistrial was “essential to preserve [the Mullinses’] right to a fair trial.” (Citation and punctuation omitted.) Milton v. State, 232 Ga. App. 672, 676 (503 SE2d 566) (1998).
Judgment reversed.
Johnson, C. J, Pope, P. J., and Ellington, J., concur and concur specially. Blackburn, P. J., Eldridge and Barnes, JJ., dissent.In addition, this “issue” is unsupported by the record. Appellants argue that the chain of custody is clouded by a notation in the lab report that prior to its analysis by Ali, the evidence was received from “T. Pitts,” whose identity is unknown, of the Dawson County district atttomey’s office, where the drug task force was located. But the report states only that a request was received from Pitts to reanalyze the evidence and not, as urged by appellants, that the evidence was received from Pitts.