BAZELON, Chief Judge.
In Naples v. United States, 113 U.S. App.D.C. 281, 307 F.2d 618 (1962) (en banc), we reversed appellant’s conviction of murder in the first degree, murder in the second degree, housebreaking and petty larceny. Upon retrial he was convicted of murder in the first degree, murder in the second degree, and housebreaking,1 and the jury unanimously recommended life imprisonment. He again seeks reversal.
I.
We consider first the admissibility of confessions which, according to two police officers, were made by appellant in the following circumstances. Immediately after his arrest, appellant was brought [510]*510to the Ninth Precinct Police Station and taken to the second floor office of Lieutenant Culpepper, who testified:
“I told the defendant that I was a police officer, and that he did not have to talk to me unless he wanted to.
“He replied, ‘I know that.’
“I asked him if he had done something that he knew to be wrong, and if he wanted to tell me about it.
“And he said, ‘About what? ’
“And I said, ‘Have you done something that is wrong and that you are ashamed of and want to tell the truth about?'
“And he said, ‘Do you mean about the lady? ’
“And I said, ‘Yes.’
“He said, ‘Well, I was prowling in the hallway,’ and I interrupted and said, ‘What hallway? ’
“He said, ‘The hallway in the apartment next to where I live.’
“And I said, ‘Where do you live ? ’
“He replied, ‘The 200 block of Massachusetts Avenue, Northeast.’
“I asked him to continue. He then said that he was prowling in the hallway, looking for something to steal; that he was standing in front of the mail boxes, when he noticed that the last apartment on that floor, the first floor, was ajar; the door was not closed.
“He walked over to the door and stood there for some time, and became aware that no one was in the apartment. He said he knew no one vras in the apartment because they would have heard him, had there been someone there. He went into the apartment, looked through the apartment and searched it. He found, took two dollars from a drawer in a small table.
“He was looking into a closet, when a white lady came in. She stood at the door and shouted and said, ‘What are you doing here,’ and threw her pocketbook at him, and at the same time said, ‘Get out of here.'
“He related then that everything went dark, and then the next thing he realized was that he was leaning over the lady. She was on the floor. He saw lots of blood and he had blood on his hands, and he knew that he had hurt her.” [Emphasis supplied.]
On the former appeal, we held the substance of this testimony was not excluded by Mallory v. United States, 354 U.S. 449, 77 S.Ct. 1356, 1 L.Ed.2d 1479 (1957). Naples v. United States, 113 U.S.App.D.C. 281, 307 F.2d 618 (1962).2 Without considering the merits of this holding, we apply it as the law of the case to sustain admission of this testimony.
At the second trial there was testimony of further admissions not offered at the first trial. After appellant had finished his statement to Culpepper, he was taken from Culpepper’s second-floor office to a room on the first floor for booking, and returned to Culpepper’s office ten to fifteen minutes later. Captain Hartnett then arrived. He testified:
“Well, after he [Culpepper] introduced the defendant, Lieutenant Culpepper, in his [the defendant’s] presence, then told me that he had talked to the defendant and that he told him that he was the one who had been in the apartment on Massachusetts Avenue and had the trouble with the woman. **-«•***
“Q. What else was said or done at that time by anyone?
[511]*511“A. Well, after Lieutenant Cul-pepper had run through in substance, what the defendant had told him, I told him I had a couple of questions I wanted to ask him.
“Q. Now, what exactly, did the Lieutenant run through, if you can recall ?
“A. Well, the substance of it was—
“Mr. Nordlinger [Defense Counsel] : This, of course, is over our objections for the reasons discussed at the bench, Your Honor.
“The Court: All right. Denied.
“The Witness : That the defendant had told him that he lived in the next apartment to 225, he lived next door; that he had gone into 225 Massachusetts Avenue to look around, that he noticed the apartment door was slightly open, he went into this apartment, he looked around and started going through things. While he was in there the woman came in on him and that he struck her several times, and, well, that’s about the gist of it.
“By Mr. Smithson:
“Q. He said he struck her several times ?
“A. He struck her a couple of times.” [Emphasis supplied.]
Captain Hartnett’s testimony differed from Lieutenant Culpepper’s in one crucial respect. Culpepper testified that appellant said he had no memory of hurting the woman. Hartnett testified that Cul-pepper told him, in appellant’s presence, that appellant had said he “struck her several times” or “a couple of times.” Since appellant’s defense of insanity rested largely on his claim that, because of an epileptic seizure when the woman entered the room, he remembered nothing, the prosecution relied heavily on Hart-nett’s testimony to show that appellant did remember.
Defense counsel objected to the admission of Hartnett’s testimony on Mallory grounds. He urged that the Hartnett interview took place after the initial statement to Culpepper and during a period of unreasonable delay. In overruling this objection, the trial court said the admissions to Culpepper and to Hart-nett were “one continuous confession or admission.” We need not rule on this point, because we think this testimony by Hartnett is hearsay and appellant’s assent to the statement that “he struck her” was not clear enough to allow Hart-nett’s testimony under the adoptive admission exception to the hearsay rule.
Hartnett did not testify that appellant said to him that appellant struck the woman. Hartnett testified that Culpep-per recounted to Hartnett, in appellant’s presence, that appellant had admitted to Culpepper that he struck the woman. This was double hearsay. . Before the jury, Hartnett did not testify that appellant affirmatively agreed to the statement that he struck the woman. But the jury may have inferred that appellant remained silent and may have thought that appellant thereby agreed to Culpep-per’s statement, as reported by Hartnett, that appellant said he struck the woman. Earlier at a hearing not in the presence of the jury, on the question of this testimony’s admissibility, Hartnett had testified that, after Culpepper had completed his resume of appellant’s admissions, “I turned to the defendant and I said, ‘Is what * * * the Lieutenant said right?’ He nodded his head ‘Yes.’ ”
“Multiple hearsay is, of course, even more vulnerable to all the objections which attach to simple hearsay, and it seems that if it is to come in at all, each of the out-of-court statements must satisfy the requirements of some exception to the hearsay rule.” McCormick, Evidence § 225, at 461 (1954). The only exception which could be considered here is the one regarding adoptive admissions. Testimony that an accused adopted statements of another person as his own admissions may be let in under this exception if it clearly appears that the accused understood and unambiguously assented to those statements. Skiskowski v. United States, 81 U.S.App.D.C. 274, 158 [512]*512F.2d 177 (1946), cert. den. sub nom., Quinn v. United States, 330 U.S. 822, 67 S.Ct. 769, 91 L.Ed. 1273 (1947).3 “ * * * [T]he question of fact whether the party’s conduct manifested his assent to the statement of the other person is a preliminary question for the judge. Unless he so finds, the statement is excluded.” 4 In the present case, the trial court was not requested to consider this question and it did not.
It also appears that if testimony is allowed as an oral adoptive admission, the jury should be cautioned “against trusting overmuch to the accuracy of such testimony,” since there are “great possibilities of error in trusting to recollection-testimony of oral utterances, supposed to have been heard. * * *” 7 Wigmore, Evidence § 2094, at 468 (3d ed'. 1940).5 But no such instruction was sought or given here.
We think the record does not permit a fair inference that appellant agreed to the statement that he had “struck the woman.” Appellant, described by a Government witness as having a “low average” intelligence quotient, had been arrested and taken to a police station, interviewed by one officer in a private room, taken downstairs to be booked by another officer, and returned upstairs to be confronted by yet another officer. Appellant then allegedly heard Culpepper tell Hart-nett that appellant admitted the following: that he lived next door to 225 Massachusetts Avenue, that he had gone into 225 Massachusetts Avenue to look around, that he noticed the apartment door was slightly open, that he went into this apartment, that he looked around and started going through things, that while he was there the woman came and that he struck her several times. Appellant allegedly responded to this lengthy statement either by remaining silent or by nodding his head “Yes.” Either response gives little assurance that appellant adopted, as his own admission, every detail of the statement or, more particularly, that he adopted the statement that “he struck her.”
Moreover, Culpepper flatly contradicted Hartnett’s testimony. Culpepper testified that appellant himself repeated his admissions in full to Hartnett, and that [513]*513appellant consistently maintained that he had no memory of the stabbing. Since Hartnett testified that Culpepper had said appellant admitted striking the woman, Culpepper’s denial that appellant made such a statement casts great doubt on whether appellant agreed to the statement “he struck her.” The contradiction between the Government witnesses hardly provides clear evidence of assent.
We therefore hold that Hart-nett’s testimony, under discussion here, is inadmissible as a matter of law. We make this determination, rather than remand for the trial court’s consideration, because we are “of clear opinion” 6 that under no reasonable view of the record can it be said that appellant unambiguously and comprehendingly assented to the statements which Hartnett attributed to him.
The error we discuss was not raised below or in this court. Nevertheless, we think reversal is authorized by the “plain error” rule, Rule 52(b), Fed.R.Crim.P., since the prosecution urged the erroneously admitted testimony to discredit an essential aspect of appellant’s insanity defense which was his primary if not only defense.7
II.
Appellant contends that the housebreaking and felony murder charges should be dismissed because there was insufficient corroboration of his admission to Lieutenant Culpepper that he entered the deceased’s apartment building “looking for something to steal,” and because this intent to steal at the time of entry is an essential element of both offenses.
A confession must be corroborated by extrinsic evidence. Opper v. United States, 348 U.S. 84, 75 S.Ct. 158, 99 L.Ed. 101 (1954); Smith v. United States, 348 U.S. 147, 75 S.Ct. 194, 99 L.Ed. 192 (1954). Some courts have required that every essential element of the confession be corroborated8 while other courts have required merely that enough of the confession be corroborated to establish its general trustworthiness.9 The Supreme Court has established only (1) that the prosecution must present some extrinsic evidence to corroborate a confession, and (2) that the corroborative evidence need not be sufficient, exclusive of the confession, to establish guilt beyond a reasonable doubt. Opper v. United States, supra; Smith v. United States, supra. But beyond these two broad propositions, “ * * * it is not clear what quantum of corroboration is required or to what matters the corroboration must relate.” Fisher v. United States, 324 F.2d 775, 778 (8th Cir. 1963).
Minimal corroboration of confessions may be sufficient to avoid the dangers of conviction based on false confessions induced by some inner compulsion.10 But it may not always be sufficient to pre[514]*514serve the integrity of our system of criminal justice. As the Supreme Court has recently reemphasized, “We have learned the lesson of history, ancient and modern, that a system of criminal -law enforcement which comes to depend on the ‘confession’ will, in the long run, be less reliable and more subject to abuses than a system which depends on extrinsic evidence independently secured through skillful investigation.” Escobedo v. United States, 378 U.S. 478, 488-489, 84 S.Ct. 1758, 1764, 12 L.Ed.2d 977 (1964). Thus, sufficient extrinsic evidence should be required to preserve the integrity of the right against self-incrimination, the presumption that every accused is innocent until his guilt is established beyond a reasonable doubt and the accusatorial nature of our system.
We think the extrinsic evidence of appellant’s intent to steal when he entered the premises is sufficient. First, the evidence regarding the position of the body near the door, the knife wounds, the charred gloves on the apartment stove, all directly corroborate important details of appellant’s admissions. Next, extrinsic evidence regarding drawers and closets pulled open and apparently searched, and an empty wallet found by police in full view on the sofa, indirectly or inferentially corroborate appellant’s admissions that he attempted to steal something in the apartment. Third, the circumstances of appellant’s initial entry into the apartment are corroborated. Appellant admitted that when he approached the apartment, the door was ajar and the apartment was unoccupied; there was testimony that the deceased had left her apartment to return a borrowed key to the resident manager’s apartment on the next floor, and it is a fair inference that deceased left the door to her apartment ajar for this short errand. This evidence corroborates appellant’s admissions regarding the stabbing, his attempting to steal after he entered, and his entry when the ápartment was empty and the door ajarJ We think it is also sufficient to support a jury inference of intent to- steal upon entry. It might not be sufficient to corroborate appellant’s admission that he actually found money in the apartment.11 But a subjective fact like intent to steal cannot be proved by direct evidence as objective facts such as possession of stolen property can.12 Corroboration of intent must necessarily rest largely on inference.
III.
Appellant contends the trial court should have directed a verdict of not guilty by reason of insanity. He advances two arguments. The first is that the Government introduced insufficient evidence to counter appellant’s insanity defense. This insanity defense was persuasive. Appellant’s mother, his teacher (Mrs. Leaf), and others testified to recurring “blackouts.” A physician from District of Columbia General Hospital testified that appellant had an epileptic seizure during an electroencephalogram test. Appellant’s history indicated that he spoke nothing but gibberish until he was eight years old; he was placed in special classes for disturbed and retarded children throughout his public schooling; and his intelligence quotient registered in various tests from 65 to 69. Testimony by expert and lay witnesses showed appellant’s emotional instability and impulsiveness ; he had been discharged from the armed services for mental deficiency; he had threatened his sergeant with a rifle, and at times he apparently had the delusion that he had killed the sergeant. But, on the other hand, experts for the Government testified that there was no record of any epileptic seizure during appellant’s two-year con-
[515]*515The Government psychiatrists testified that, although they thought appellant sane, other competent experts could think him insane. But it does not follow, as appellant contends, that the jury must necessarily have had a reasonable doubt on the issue. A psychiatrist’s opinion “lies in estimate only and is the result of a balancing of concrete data.” 7 WiGMORE § 1976, at 121. The jury is free to believe any reasonable “estimate” even though different or contrary views may also be reasonable. Carter v. United States, 102 U.S.App.D.C. 227, 236, 252 F.2d 608, 617 (1957); McDonald v. United States, 114 U.S.App.D.C. 120, 312 F.2d 847 (1962) (en banc).
IV.
A lay witness, Mrs. Leaf, testified that she had been a teacher of “exceptionally disturbed children” for fifteen years in the public school system where she taught appellant from September 1951 until June 1952. On direct examination, after testifying about appellant’s conduct she had observed, Mrs. Leaf was asked: “Do you have any recollection, either independently or from the records, of the mental condition of the defendant, John Naples, at that time?” The prosecutor objected to this question and the trial judge sustained the objection because “Mrs. Leaf * * * [was] a school teacher and not a psychiatrist, not a psychologist.” Mr. Warner, custodian of the junior high school appellant attended, after, relating several incidents involving appellant, stated “that his. [the accused’s] sanity wasn’t altogether clear.” The prosecutor had objected to previous questions to Mr. Warner regarding appellant’s mental state, and when Mr. Warner made this statement, the trial court immediately admonished the jury: “You will disregard that. This Custodian is not qualified as a psychiatrist or psychologist. That is a very technical subject and it is also something the jury will have to consider from their own background.”
It was error to exclude the opinions of Mrs. Leaf and Mr. Warner.
Lay witnesses may testify upon observed symptoms of mental disease, because mental illness is characterized by departures from normal conduct. Normal conduct and abnormal conduct are matters of common knowledge, and so lay persons may conclude from observation that certain observed conduct is abnormal. Such witnesses may testify only upon the basis of facts known to them. They may testify as to their own observations and may then express an opinion based upon those observations. Of course the testimony of a lay witness with training in this or related fields may have more value than the testimony of a witness with no such training. Also obvious upon a moment’s reflection is the fact that, while a lay witness’s observation of abnormal acts by an accused may be of great value as evidence, a statement that the witness never observed an abnormal act on the part of the accused is of value if, but only if, the-witness had prolonged and intimate-contact with the accused. [Carter v. United States, 102 U.S.App.D.C. at. 237, 252 F.2d at 618, emphasis supplied.] 14
[516]*516The court erred also in excluding evidence of a judicial determination that appellant was not competent to stand trial.15 In Lyles v. United States the majority of this court held that if the defense introduced a judicial finding of incompetency to stand trial, the prosecution could then introduce a later judicial finding of competency to stand trial. Both the majority and the dissenting judges assumed that the judicial determination of incompetency was admissible. The dissenting opinion stated, “ * * * incompetency to stand trial, though not the same as insanity, is relevant to it * * 103 U.S.App.D.C. at 39, 254 F.2d at 742.
A problem regarding the trial court’s instructions to the jury on the insanity defense also deserves mention since it might arise in any new trial. Although the court in some parts of its charge correctly instructed the jury that the burden of showing freedom from mental illness rested on the prosecution, other parts of the charge implied the contrary. The court said:
“The problem for you is whether the accused was suffering from a mental disease or defect * * * and if yon find that he was, whether there was a relationship between such disease or defect and the specific alleged criminal acts and if so, whether that relationship was such as to justify a reasonable inference that the accused would not have committed the acts if he had not had the disease or defect.” [Emphasis supplied.]
Here and elsewhere in his charge, the judge intimated that in order to acquit on the ground of insanity the jury must affirmatively find a mental disease or defect and a causal relationship with the criminal act. Compare Carter v. United States, 102 U.S.App.D.C. 227, 252 F.2d 608 (1957); Wright v. United States, 102 U.S.App.D.C. 36, 250 F.2d 4 (1957). Though it is difficult, it ir also necessary, to cast instructions continually in terms of the Government’s burden to show sanity beyond reasonable doubt. The obligation rests on counsel as well as the court to see that the jury is not confused in this matter.
“In order to convict, the jury must be convinced beyond a reasonable doubt either (1) that the accused had no mental disease or defect or (2) that, although the accused was defective or diseased, his act was not the product of the affliction. Or, to state the matter otherwise, the jury must acquit unless it is convinced beyond a reasonable doubt that the alleged criminal act was not the product of a mental disease or defect. [Carter v. United States, 102 U.S.App.D.C. at 234, 252 F.2d at 615.]”
V.
We think the court erred in refusing to instruct the jury that it could not find appellant guilty of both first degree and second degree murder. Since the jury found appellant guilty on both counts, the error must be deemed prejudicial.
Sections 22-2401-02, District of Columbia Code (1961), define first degree murder.16 Section 22-2403 provides : “Whoever with malice afore[517]*517thought, except as provided in sections 22-2401, 22-2402, kills another, is guilty of murder in the second degree.”17 (Emphasis supplied.) This makes it clear that a singlé offense cannot be both first and second degree murder. In Goodall v. United States, we said an instruction on both first and second degree murder.
“is necessary only when from the evidence as a whole the jury might reasonably find the defendant guilty of either first or second degree murder, and therefore must decide which degree had been committed.” [86 U.S.App.D.C. 148, 151, 180 F.2d 897, 400, 17 A.L.R.2d 1070 (1950), cert. denied, 339 U.S. 987, 70 S.Ct. 1009, 94 L.Ed. 1389 (1950), emphasis supplied.]
“At common law there were no degrees of murder. All homicide with malice aforethought, whether express or implied, was murder. And all murder was punished by death.” Clark & Marshall, Crimes § 10.09 at 608 (6th ed. 1958). By statute murder was defined in various degrees in order to treat criminal behavior on a more individual basis. “First degree murder” now stands as the criminal act deserving the most severe sanction. To permit conviction of both first and second degree murder for the same offense would be contrary to the intent of the nineteenth century legal reforms which displaced undifferentiated common law murder.
If it is improper to sentence appellant for both first and second degree murder, as our dissenting brother apparently concedes, it seems to us also improper to instruct the jury that they can find guilt on both counts. Our brother says an instruction which requires a choice would confuse the jury. The jury may also be confused by instructions about “premeditation” or “malice” as elements distinguishing one degree of murder from another; but this would hardly justify a refusal to instruct the jury that it could not convict for both greater and lesser degrees of a single offense.18
VI.
In the prosecutor’s closing argument, he said to the jury: “Whether there was or was not [blood] on any clothing that was worn by defendant at that time, you don’t know, and I don’t know. One man knows. He sits there.” Defense counsel moved for a mistrial on the ground that this called attention to appellant’s failure to testify. The trial court denied the motion but gave an immediate corrective instruction to the jury. We need not decide whether a mistrial should have been granted since we order a new trial on other grounds.
Appellant contends that because the jury unanimously recommended life imprisonment, he may not be sentenced to death if at a new trial he is again found guilty of first degree murder. This contention involves constitutional ques[518]*518tions,19 which we should consider only if it becomes necessary to do so.
Reversed and remanded for a new trial.