KILEY, Circuit Judge.

A jury found defendant Matos, a postal employee, guilty, under two separate counts of the indictment, of two thefts from the mail in violation of 18 U.S.C. § 1709. Matos has appealed from the judgment on the verdict and concurrent sentences of five years on each count. We reverse and remand for a new trial.

Matos had been a postal employee for more than two years when he was arrested for theft of two watches from packages in the mail. He was at the time working as a dockman engaged in loading sacks of Hawaii-bound mail into trailers from a conveyor which brought the sacks to the trailer from a chute leading from the post office. There is evidence that on the two occasions subject of the indictment three postal inspectors, from a hidden place above the dock, observed Matos. It is substantially undisputed that on both days they saw Matos pick up a "test marked" package containing a watch, which package had fallen from the specially identifiable mail bags that had been left partially open by the inspectors. Matos, on both occasions, then placed the package inside the trailer and went behind a mound of bags, apparently out of the view of the inspectors. The inspectors did notice movement at the top of the load. The watch placed in the test package on the first occasion was missing from the sack when the trailer arrived in Honolulu. The watch on the second occasion was turned over by Matos to the inspector after they apprehended him.

I.

The only issue on appeal is whether a new trial should be ordered because Matos' Fifth Amendment right to remain silent was violated by admission into evidence of an unresponsive statement by a postal inspector to a question by the government attorney.

Inspector Mesics, testifying in the government's case in chief, began to tell what happened in Inspector Bottker's office in the post office building, to which Matos was brought after being apprehended. Matos' attorney, anticipating "troubled waters," moved for a voir dire hearing. At the hearing testimony developed that Matos, having been given the Miranda warnings, requested a lawyer and refused to sign a waiver. Matos' attorney's anticipatory objection and motion for mistrial were overruled. And the government attorney promised to avoid "trouble waters" at resumption of trial.

After the voir dire was concluded, Mesics testified, in the presence of the jury, about the giving of Miranda warnings by Bottker, and that Matos, on request, emptied his pockets and uncovered the watch taken on the second occasion. Inspector Bottker then corroborated Mesics' testimony. He told Matos he was under arrest, read the warnings to him, and offered him for signature a waiver of rights form. The government attorney then asked, "Now, after this, did you tell defendant anything?" Bottker answered that Matos "indicated he did not desire to make a statement." Matos' attorney objected and moved for a mistrial. The district court overruled the objection and denied the motion, and then denied a motion to caution the jury to disregard the unresponsive part of Bottker's answer.

The violation of Matos' Fifth Amendment right to silence is plain. Miranda v. Arizona, 384 U.S. 436, 468, n. 37, 86 S.Ct. 1602, 16 L.Ed.2d 694 (1964); United States v. Nielsen, 392 F.2d 849, 853 (7th Cir. 1968). It was constitutional error to admit the testimony that Matos desired not to make a statement. We hold that Matos' Fifth Amendment right not to incriminate himself was violated by the admission into evidence of the postal inspector's comment, and the error was compounded by the trial court's refusal to instruct the jury that the Bottker statement should not be considered as evidence.

II.

The government argues that if what occurred is error it was harmless, citing Chapman v. California, 386 U.S. 18, 87 S.Ct. 824, 17 L.Ed.2d 705 (1967). Under Chapman the government has the burden of demonstrating to us beyond a reasonable doubt that the constitutional error did not contribute to Matos' conviction; that "before a federal constitutional error can be held harmless, the court must be able to declare a belief that it was harmless beyond a reasonable doubt." Id. at 24, 87 S.Ct. at 828. The government relies, for meeting its burden, upon the "conclusiveness" of the evidence against Matos so as to invoke the rule in Harrington v. California, 395 U.S. 250, 89 S.Ct. 1726, 23 L.Ed.2d 284 (1969), and this court's decisions in United States v. Allsenberrie, 424 F.2d 1209 (7th Cir. 1970); United States v. Wick, 416 F.2d 61, 62 (7th Cir.) cert. denied 396 U.S. 961, 90 S.Ct. 430, 24 L.Ed.2d 425 (1969); United States v. Sutt, 415 F.2d 1305, 1308 (7th Cir. 1969); and United States v. Franke, 409 F.2d 958 (7th Cir. 1969). The application of the harmless error rule is peculiarly dependent on the facts of each case.

Matos' defense was that he had no intention of stealing the watch. He testified that while working he accidentally stepped on a box which contained the watch, and that he picked the watch up and put it in his pocket with the intention of returning it to the platform office. He further testified that after he had picked up the watch the supervisor told him to go to lunch and that he was apprehended at the second floor time clock after "punching out" for lunch. He was then brought to the inspector's office where he was arrested and confronted by the three inspectors.

Matos stated that he did not take the watch to the supervisor because the supervisor left right after telling him to go to lunch and because he had been instructed to take lost articles which he found to the platform office in person, not to give them to the supervisor. He testified that he was arrested before he had a chance to go to the platform office.

The record is not clear whether Matos could or could not understand English. There was evidence that he filled out his job application in English. Yet at the conference inspectors called a Spanish interpreter to aid their discussion with him. Two character witnesses testified to Matos' good reputation for truthfulness, honesty and integrity.

The vital question for the jury was Matos' credibility in his testimony that he did not intend to steal the watch. Although there was sufficient evidence for a jury to discredit Matos' explanation of his actions, we cannot, under the circumstances mentioned above, declare a belief that, absent the Bottker unresponsive answer — highlighted by Matos' counsel's forced objection and motions for mistrial and cautionary instruction in front of the jury — no juror could have entertained a reasonable doubt that Matos, had he not been intercepted at the time clock, would have turned in the watch after lunch.

The government's reliance on Allsenberrie, Wick, Sutt, and Franke is misplaced. In Allsenberrie, defendant admitted to government agents knowledge of cartons stolen in commerce but refused to tell where they were, relying on his Fifth Amendment right to remain silent. The court ruled that the comment on the silence was harmless since there was no dispute that defendant was the "dockman" who handled the shipment of the cartons which were located in a valid search, and defendant effectually admitted that he knew of the whereabouts of the missing cartons. In Wick, an agent testified that he heard another agent ask defendant, after Miranda warnings, whether he obtained counterfeit notes, and that defendant refused to answer. This conversation was "briefly mentioned" in argument to the jury. This court held these incidents, "amidst the overwhelming evidence" against Wick, including two positive identifications, could not have contributed to the jury verdict. In Sutt, the district court admitted three in-custody statements against Sutt. In two of these Sutt was not given Miranda warnings, and in the third he was warned. The three statements he gave FBI agents were exculpatory, but the third statement, which was made after the Miranda warnings were given, was more detailed and incriminating. The court held the defendant was not prejudiced by the introduction of the first two statements. Also, the statements in that case were not so directly on a precisely vital question of intention as the unresponsive answer of Bottker here. There was a strong web of circumstantial evidence against Sutt. We affirmed on that record. Franke did not involve a Miranda question. The question there was whether incriminating information established probable cause for Franke's arrest. The government introduced into evidence, for the purpose of corroborating the informer's tip, testimony of federal agents regarding what they heard through electronic eavesdropping. We assumed, but did not decide, there was constitutional error in the admission of the fruits of eavesdropping, but sustained the arrest because the "information" given by the "informer" without regard to the eavesdropping evidence was sufficient to establish probable cause, and there was no evidence to refute the incriminating testimony of the informer at the trial.

In aid of a new trial for Matos we point out that the Miranda warning testimony was unnecessary proof in the case. There was no introduction into evidence of a confession or incriminating statement that required proof of the warning. The proof of Matos' employment, what the inspectors saw him do, the uncovering of the watch and identifying it as having been the one test mailed, were the elements of the offense charged. 18 U.S.C. § 1709. See Byram v. United States, 25 App. D.C. 546 (1905). Adducing unnecessary Miranda testimony opens the door to possible prejudice of a defendant. Moreover, when the door is opened, risks arise that what happened here may happen. It seems to us that the inspector who volunteered the prejudicial statement knew of the Miranda decision, since he had given Matos the warning. We presume that he knew that a prime purpose of the Supreme Court in Miranda is to "guarantee full effectuation of the privilege against self-incrimination." Johnson v. New Jersey, 384 U.S. 719, 729, 86 S.Ct. 1772, 1779, 16 L.Ed.2d 882 (1966). He should have known that his volunteered statement ran counter to that purpose.

Reversed and Remanded for New Trial.