WILLIAMS, J.

Blood stains and drag marks led police from two bound and gagged dead bodies found in an alley to defendant's apartment. On request of the police to enter and look around, defendant opened his apartment door resulting in the search of the apartment's rooms and defendant's questioning and arrest.

Defendant claimed 11 different trial errors, of which we find it useful to discuss only the following 5:

(1) Was there error in instructing the jury that the killings were murder in the first degree as a matter of fact and law?

(2) Was it error to limit the scope of a Brady hearing so as to preclude cross-examination of one prosecutor and the appearance of another requested by the defense concerning alleged promises to a prosecution witness?

(3) Was it erroneous for the trial judge to refuse to rule whether defendant's suppressed confessions could be used to impeach him if he testified?

(4) Where the trail of evidence seemed to lead to defendant were Miranda warnings required before the police began questioning defendant?

(5) Was error committed in admitting evidence seized as a result of the warrantless search of defendant's apartment?

We answer all but question (5) in the affirmative and reverse and remand for a new trial.

I — Facts

Following their discovery of two bodies in an alley early in the morning of June 8, 1971, Detroit police officers followed a trail of blood stains and drag marks into a nearby apartment building. With the assistance of the apartment manager, they searched the basement and three of the four apartments without a warrant. Upon reaching the fourth apartment, belonging to defendant, the officers testified they "stated [to defendant] that we would like to come in and take a look around." The police thereupon entered and made an extensive search. They found a pair of blood-stained trousers soaking in the sink. When the police first asked defendant about the trousers, he said they were his, and the blood was his from a cut from a lawn mower. A policeman then said "if the blood on those trousers matched the blood from the two bodies found in the alley, he [defendant] was going to be in trouble." Defendant then changed his story and said he had found the trousers and taken them because they appeared to fit. Defendant was then arrested and after that given his Miranda warnings.

Defendant was tried by a jury for first-degree murder on separate informations for each decedent. Among witnesses for the prosecution were two individuals who testified they had assisted defendant. Apparently neither was ever imprisoned for his role, and the case against at least one was dropped. Defendant did not testify.

The jury returned a verdict of murder in the first degree in both cases on March 21, 1972. The Court of Appeals affirmed on August 30, 1973. 49 Mich. App. 308; 212 N.W.2d 41 (1973). Defendant claimed 11 errors including the 5 heretofore set forth above.

II — Was There Error in Instructing the Jury That the Killings Were Murder in the First Degree as a Matter of Fact and Law?

In instructing the jury, the trial judge stated:

"I am going to describe for you or define for you briefly what the charge of murder encompasses. The reason I am not going to go into it with you in any more extensive detail is the fact that there has been no dispute about the fact here that the offense charged, that is murder in the first degree, is the offense that was committed. The issue, of course, will be whether the defendant is guilty of committing that offense. Now, murder at common law, and as charged in this Information, is defined as being where a person or persons of sound memory and discretion wilfully and unlawfully kill any human being against the peace of the state with malice aforethought expressed or implied. Murder of the first degree is a killing done wilfully and with premeditation. And when we talk about premeditation, we mean to consider or plan the act of killing beforehand. And as I have said, I am instructing you both as a matter of fact and as a matter of law in connection with these proceedings, that the killings here are murder in the first degree." (Emphasis added.)

Defendant objected to this instruction.

The Court of Appeals, in finding no error, emphasized certain statements of defense counsel in his opening remarks as follows:

"You will be asked in this case to decide whether Mr. Reed is guilty of their murder. That will be the question. Not whether or not the people died. Not whether or not these people were murdered. That they met their death unnaturally, I think that will be quite clear." (Emphasis added.) 49 Mich. App. 308, 327.

The Court of Appeals then pointed out that the defense theory throughout was alibi. It concluded that that theory and defense counsel's above statement created no prejudice, although the court's instructions "limited the jury's consideration to a question of identification of the perpetrator of the crime, where the fact that the crime had been committed was not in dispute." 49 Mich. App. 308, 328.

This is not the law.

Once a plea of not guilty is entered, the defendant "has an absolute right to a jury determination upon all essential elements of the offense. This right, emanating from the criminal defendant's constitutional right to a trial by jury, is neither depleted nor diminished by what otherwise might be considered the conclusive or compelling nature of the evidence against him. * * * [F]urthermore, in a situation wherein an understandingly tendered waiver is not forthcoming from the defendant, under no circumstances may the trial court usurp this right by ruling as a matter of law on an essential element of the crime charged." United States v England, 347 F.2d 425, 430 (CA 7, 1965). (Footnote omitted.)

The trial judge must carefully ensure that there is no trespass on this fundamental right.

The instruction to the jury must include all elements of the crime charged, People v Liggett, 378 Mich. 706, 714; 148 N.W.2d 784 (1967); People v Pepper, 389 Mich. 317, 322; 206 N.W.2d 439 (1973), and must not exclude from jury consideration material issues, defenses or theories if there is evidence to support them. 22 Michigan Law Practice, Trial, § 236, p 386.

In the instant case, the trial court charged:

"[T]here has been no dispute about the fact here that the offense charged, that is murder in the first degree, is the offense that was committed."

Such an instruction is patently wrong. The presence of two dead bodies alone cannot reveal the state of mind of the killer nor the full circumstances of the killing. Without such additional evidence it is impossible to know what degree of homicide was committed.

Obviously it cannot be presupposed, as the instruction did, that first-degree murder was involved for two reasons. First, it cannot logically be presumed that it was murder in the first degree without knowing that the killer had the necessary premeditation and intent. This would require proof beyond the existence and condition of the dead bodies. Second, it cannot legally be presumed for the reason that the necessary premeditation and intent are elements of the crime the prosecution must prove. By instructing as she did, the trial judge incorrectly removed these problems from jury consideration.

The prosecution urges us to accept the rule of People v Griffen, 36 Mich. App. 368; 194 N.W.2d 104 (1971), and cases relying thereon. In Griffen, the trial judge instructed:

"`I may say that I don't believe this jury is going to have much difficulty in arriving at the conclusion that a felonious homicide was committed, and that the homicide was second-degree murder.'" 36 Mich. App. 368, 371.

The Court of Appeals with a strong dissent by Justice (then Judge) LEVIN on another issue, found that, if there was error, it was not reversible, inasmuch as the only dispute at trial was over who committed the homicide.

We find that the right of the jury to determine all elements of an offense is so fundamental a right that the harmless error rule is not appropriate where the judge invades that province. There is a difference between commenting on the evidence and making a finding of fact for the jury. When the trial judge, as in the instant case, instructs that an essential element of a criminal offense exists, as a matter of law, we will find reversible error. Insofar as Griffen and progeny contravene this principle, they are overruled.

III — Was it Error to Limit the Scope of a Brady Hearing to Preclude Cross-Examination of One Prosecutor and the Appearance of Another Requested by the Defense Concerning Alleged Promises to a Prosecution Witness?

A principal witness against defendant was John Zellner. Zellner was charged as defendant's accomplice in the murder of Glenn Williams. Zellner's motion for bail was originally denied, but subsequently both bail and severance from defendant were granted. Zellner thereafter testified against defendant. (Ultimately, after this trial, his case was dismissed.) On the basis of these suggestive facts defendant asked for a Brady hearing to determine whether any promises had been made to Zellner to testify against defendant.

In the Brady hearing, Zellner's counsel stated he had advised a police officer and the trial prosecutor that Zellner was willing to testify against defendant but denied receiving any consideration therefor. Both the police officer and his partner denied on the stand that there was any agreement. The trial court questioned the trial prosecutor not under oath, and he denied any promises. The Chief of the Recorder's Court Division of the Prosecutor's Office, who was present when Zellner was admitted to bail, was not called upon to testify. Defense sought unsuccessfully to cross-examine the trial prosecutor and was likewise unsuccessful in calling the Division Chief to the stand.

The issue before this Court is whether the trial judge committed error when she refused to permit, during this hearing, cross-examination of the trial prosecutor or direct examination of the Chief of the Recorder's Court Division of the Wayne County Prosecutor's office.

The trial judge justified this limitation by first noting that as an officer of the court, the prosecutor would of course tell the truth, and by claiming that no connection had been established between the Recorder's Court Division Chief and the defendant-accomplice.

Defendant argues that a determination of whether the witness had a motive to falsify testimony against him, and a determination of whether the prosecution was withholding information about promises or representations made to him was crucial to the case. Once a hearing is held, he urges, it is the judge's duty to permit counsel to call all who could help reveal the truth.

In Brady v Maryland, 373 U.S. 83; 83 S Ct 1194; 10 L Ed 2d 215 (1963), the United States Supreme Court held that to secure a fair trial to the accused:

"[T]he suppression by the prosecution of evidence favorable to an accused upon request violates due process where the evidence is material either to guilt or to punishment, irrespective of the good faith or bad faith of the prosecution." 373 U.S. 83, 87.

Napue v Illinois, 360 U.S. 264, 269; 79 S Ct 1173; 3 L Ed 2d 1217 (1959), stated that:

"The principle * * * does not cease to apply merely because the false testimony goes only to the credibility of the witness. The jury's estimate of the truthfulness and reliability of a given witness may well be determinative of guilt or innocence * * *."

In the instant case, the trial judge's refusal to permit defense counsel to proceed with his questioning was based on two different reasons. Denial of the right to cross-examination of the prosecutor on the basis of the court's estimate of his credibility as a witness is improper, particularly since the Brady hearing is specifically designed to elicit information from the government and its representatives. While we agree with the trial judge that an officer of the court would not be inclined to lie, the essence of the adversary process is not to discover perjury, but rather to reveal the truth. Therefore, preventing cross-examination of the prosecutor in the instant case improperly denied counsel a most valuable tool, if not to find out what the prosecutor did, to find out what someone else did.

Denial of permission to call the Chief of the Prosecutor's Recorder's Court Division presents an issue of materiality. We hold that sufficient connection had been demonstrated in his appearance at the witness's request for bail.

As Giglio v United States, 405 U.S. 150, 154; 92 S Ct 763; 31 L Ed 2d 104 (1972), and Napue have both determined, evidence concerning the credibility of a witness is relevant toward ensuring that defendant receives a fair trial. This is still the law in Michigan. In People v Evans, 30 Mich. App. 361; 186 N.W.2d 365 (1971), the Court of Appeals found reversible error in the trial court's refusal to allow the jury to be told that defendant's accomplice and codefendant who had testified against him was permitted after testifying but before the jury went out to plead to a lesser offense. See also People v Bortnik, 28 Mich. App. 198; 184 N.W.2d 275 (1970).

Therefore, we hold that the trial judge erroneously limited the scope of the Brady hearing, and that once requested, such a hearing should include all witnesses and all evidence which can reasonably cast light on the question to be determined.

IV — Was it Erroneous for the Trial Judge to Refuse to Rule Whether Defendant's Suppressed Confessions Could be Used to Impeach Him if He Testified?

Shortly after his arrest, defendant Ike Reed, because of promises made to him by police officers, confessed to the killings. As a result of its involuntary nature, the confession was suppressed as evidence in the presentation of the people's case in chief, but the pretrial order also expressly observed that use of the statements for impeachment purposes was reserved for decision by the trial judge.

At trial, defense counsel asked the judge how she would rule if defendant chose to testify and if the prosecutor attempted to impeach him by use of the suppressed statements. She refused to make a ruling in advance, but asked for a formal offer of proof. No offer of proof was made and defendant did not testify.

The Court of Appeals, relying on Harris v New York, 401 U.S. 222; 91 S Ct 643; 28 L Ed 2d 1 (1971), and People v Graham, 386 Mich. 452; 192 N.W.2d 255 (1971), ruled that the defendant's objection to the use of the confessions for impeachment was "unfounded". 49 Mich. App. 308, 324-325. We believe the objection sound and Harris and Graham not on point.

The difference between Harris and Graham and the instant case is that the former relate to impeachment because of failure to give due Miranda warnings, and the instant case relates to involuntary confessions. In order to deter the police from breaking the law, statements made prior to the Miranda warnings are unusable to prove the elements of the crime charged. However, such statements may still be used for impeachment purposes if otherwise trustworthy. Involuntary confessions, on the other hand, may never be used, both because the police broke the law but more importantly because an involuntary confession is always of questionable "trustworthiness". Consequently, an involuntary confession, which is of questionable trustworthiness, is not a proper foundation for impeachment, whereas statements prior to Miranda warnings may be a perfectly sound foundation for impeachment. It is instructive to note Harris expressly states, "[p]etitioner makes no claim the statements made to the police were coerced or involuntary." 401 U.S. 222, 224. Furthermore, Harris permits Miranda-barred evidence to impeach "provided of course that the trustworthiness of the evidence satisfies legal standards". (Emphasis added.) 401 U.S. 222, 224.

As indicated, the impropriety in using an involuntary confession for impeachment purposes is that it is untrustworthy evidence either to prove guilt or impugn credibility. The Supreme Court of Oregon put it forcefully and persuasively in State v Smith, 242 Or. 223, 226; 408 P.2d 942, 944 (1965), as follows:

"An involuntary confession is just as untrustworthy when used for impeachment purposes as when used to prove guilt. Such a confession is of no greater credibility when used to prove defendant a liar than when it is used to prove him guilty."

We therefore hold that an involuntary confession because of its untrustworthy evidentiary value is not usable either as direct evidence or for impeachment purposes. The trial judge erred in not ruling that the involuntary confessions could not be used for impeachment, as did the Court of Appeals in supporting her.

V — Were Miranda Warnings Timely Given?

In determining whether the investigation had become accusatory and the defendant entitled to his Miranda warnings, the Court of Appeals applied the rule in People v Wasson, 31 Mich. App. 638, 642; 188 N.W.2d 55 (1971), that the "deciding factor, in each case, is determined by examining the specificity of the investigation, i.e., whether the investigation has focused on one suspect". 49 Mich. App. 308, 319. The Court of Appeals concluded there was not such focus. We approve the test employed and believe it should be used by examining the totality of the circumstances. However, we disagree with the Court's conclusion.

Following discovery of the two bodies in the alley, the police followed a trail of blood and drag marks into a four-apartment building. The dead bodies exhibited signs to the police of narcotic use and they suspected that the homicide was narcotics connected. Finding no evidence of homicide in the first three apartments, the police sought entrance into the fourth and final apartment from the manager, but his key did not fit. Officer Clemons testified that at this point defendant came down the hall and put his key into the door. Officer Clemons testified "He [the defendant] affirmed that he did live here and that we may come in". Officer Hill testified similarly. As the officers entered, from the way the door opened and the way the windows were barred and from the presence of narcotics paraphernalia, "it was at once apparent that this was a narcotics pad".

The police proceeded from the living room to the bedroom and from there to the kitchen. The bedroom floor showed it had recently been cleaned and there was a wet mop with red-tinged water on it. This caused the police to suspect that there had been blood on the floor.

The police also found some trousers soaking in red-tinged water that appeared to indicate blood. The trousers themselves seemed marked with the remains of blood stains.

At this point Officer Clemons admitted the police "had, perhaps, found the scene of the homicide" and that the defendant "perhaps knew something about" the homicide and "[m]ore than that, perhaps".

In view of narrowing their investigation down to what they believed to be the place of the homicide and to the owner of that place, the defendant, whom they believed to be connected with that homicide, by knowledge and "[m]ore than that, perhaps", the question arises whether the investigation had not "focused". This question is important because the police, without giving a Miranda warning, had the following colloquy with defendant as reported by Officer Hill:

" A. Yes, we questioned the defendant about the trousers and the suspected blood stains on them. He stated that they were his trousers and that he had injured himself while playing around with a lawn mower on Marlborough and at this time we told him that we had someone coming out from the scientific lab to check the water and the floor and the walls for blood and that if the blood on the trousers matched the blood of the deceased that we found in the alley, there might be a little trouble.

" Q. Did he make any response to this answer?

" A. Yes, he changed his statement.

* * *

" A. He changed his statement with relationship to the trousers at first.

" Q. What did he tell you about the trousers the second time?

" A. He stated the second time the trousers were not his; he found them on the rear steps, so [sic] they probably would fit him and probably meant to soak them.

* * *

" A. At this time we advised the defendant of his constitutional rights."

Before this colloquy then, we must ask ourselves, "had the investigation `focused' on the defendant?"

From the above facts there can be no question but that the investigation had "focused" on the murder site.

Had the investigation "focused" as well on "one suspect"? The defendant had the key to the apartment and was in fact entering it. When the police asked him, he said it was his apartment. The only question left was were the bloody pants the defendant's — if they were, Officer Hill indicated that would tend to link defendant with the murders.

The ultimate question then really is whether the interrogation about defendant's ownership of the trousers was merely preliminary exploration or was it the "clincher"? Looking at all the facts, the latter alternative seems by far the more reasonable.

As a consequence we hold that the investigation had focused on defendant before the trouser-ownership question was asked and that the defendant therefore should have been given a Miranda warning before that question was asked.

VI — Was the Search Reasonable as One to Which Defendant Gave His Valid Consent?

Defendant made a pretrial motion to suppress certain incriminating evidence seized by police officers in his apartment, contending that, as he did not know he could refuse permission for them to enter, he did not knowingly waive his Fourth Amendment rights and validly consent to the search.

At the evidentiary hearing, testimony was received from police officers and the apartment manager that the police, without a search warrant, had, upon their discovery of the bodies in the alley and the drag marks and blood stains leading into the building, followed that trail, and, with the aid of the apartment manager, investigated three of the four apartments, finding nothing to connect them with the homicides.

When the apartment manager's key would not fit into the lock of the fourth apartment, belonging to defendant, the police were in the manager's office, directly across the hall, telephoning the scientific laboratory for assistance. Defendant fortuitously appeared at the door and placed his key in the lock. The police approached him, and, according to their testimony and that of the manager, identified themselves and asked if they might come in and look around. They said defendant was not only courteous and genial, but also pointed out places to look. They indicated that at no point was he restrained and that defendant was not given his Miranda rights at that time because he was not suspected of anything. There were initially at least three, and perhaps four, officers in the apartment, with the number of police personnel, including those from the lab, finally totaling ten.

Defendant, however, testified that he was ordered to open the door by two detectives and two patrolmen, that he insisted on their showing him a search warrant, and that they pushed their way into the apartment. Once they were inside, he said there was a "fight" (which he defined as not physical) in which he again demanded to see a warrant and the police forced him to sit down while they searched.

At the conclusion of the evidentiary hearing, the court ruled that defendant had validly consented to the search of his apartment. The Court of Appeals affirmed.

A warrantless search and seizure is unreasonable per se and violates the Fourth Amendment of the United States Constitution and art 1, § 11 of the state constitution unless shown to be within one of the exceptions to the rule. 20 Michigan Law Practice, Searches Seizures, § 2. The burden is always on the state to show such an exception exists. People v Chism, 390 Mich. 104, 123; 211 N.W.2d 193 (1973). Coolidge v New Hampshire, 403 U.S. 443; 91 S Ct 2022; 29 L Ed 2d 564 (1971).

In the instant case, the government argues that defendant's valid consent rendered the search reasonable. "Whether a consent is valid is a matter of fact based upon the evidence and all reasonable inferences to be drawn from it." 390 Mich. 104, 123. The presence of coercion or duress would require a finding that consent was not given. People v Kaigler, 368 Mich. 281, 294; 118 N.W.2d 406 (1962).

The Court of Appeals correctly noted that the United States Supreme Court has rejected defendant's contention that knowledge of the right to refuse admittance to police is required before consent to a search can be considered valid. The law today is that knowledge of the right to refuse is but one factor in the totality of circumstances to be examined in construing the reasonability of a search.

"[W]hen the subject of a search is not in custody and the State attempts to justify a search on the basis of his consent, the Fourth and Fourteenth Amendments require that it demonstrate that the consent was in fact voluntarily given, and not the result of duress or coercion, express or implied. Voluntariness is a question of fact to be determined from all the circumstances, and while the subject's knowledge of a right to refuse is a factor to be taken into account, the prosecutor is not required to demonstrate such knowledge as a prerequisite to establishing a voluntary consent." Schneckloth v Bustamonte, 412 U.S. 218, 248-249; 93 S Ct 2041; 36 L Ed 2d 854 (1973).

Refusing to apply the Johnson v Zerbst standard that the state must demonstrate "an intentional relinquishment or abandonment of a known right or privilege" in order to show consent to a search, 412 U.S. 218, 238-245, the Court in Schneckloth indicated these general principles should be followed:

(1) "While the Fourth and Fourteenth Amendments limit the circumstances under which the police can conduct a search, there is nothing constitutionally suspect in a person's voluntarily allowing a search." 412 U.S. 218, 242-243.

(2) "[U]nlike those constitutional guarantees that protect a defendant at trial, it cannot be said every reasonable presumption ought to be indulged against voluntary relinquishment." 412 U.S. 218, 243.

(3) "[T]he community has a real interest in encouraging consent * * *." 412 U.S. 218, 243.

(4) A waiver approach is unrealistic in "the informal, unstructured context of a consent search", and would be inconsistent with third-party consents. 412 U.S. 218, 245.

(5) Absent evidence of inherently coercive tactics, either from the nature of police questioning or conduct, or the environment and atmosphere in which events occur, traditional tests for determining voluntariness of consent will apply. 412 U.S. 218, 247.

(6) "[T]he failure to require the Government to establish knowledge as a prerequisite to a valid consent" will not "relegate the Fourth Amendment to the special province of `the sophisticated, the knowledgeable and the privileged.'" 412 U.S. 218, 247-248.

Analogizing to the problem of coerced confessions, the Court found these criteria did not turn on the presence or absence of a single factor, but required careful scrutiny of the totality of all the surrounding circumstances. Applying these Schneckloth criteria, we find the following facts made up the relevant circumstances:

(1) The police followed a trail of blood stains and drag marks from two bodies into an apartment building and had already searched all other apartments when they reached defendant's. They had no search warrant.

(2) The apartment manager tried to let the police enter defendant's apartment, but his key would not work.

(3) The police were in the doorway of the manager's apartment, directly across the hall, when they saw defendant come to his door and insert his key.

They say they identified themselves, asked whether defendant lived there, and when he answered yes, asked if they could come in and look around. They did not give defendant Miranda warnings at that time, nor did they advise him of his right to refuse admission. They also did not tell him why they were there.

The police say defendant granted permission for the police to enter and look around. Defendant claims he was forced to let the police in and asked to see a search warrant.

(4) The police made one hasty swing through the apartment, then made a more careful search, with the aid of persons from the scientific bureau. There were at least six police officers and three members of that bureau in the apartment with defendant.

(5) Defendant was given his Miranda rights after the police questioned him about bloody trousers found soaking in water in the sink. At that time he was arrested. The search was still proceeding.

(6) Following their initial entrance into the apartment, the police asked other officers and the scientific personnel to enter. Defendant was never asked if these additional people could come in and search.

(7) The police testified that defendant was not only free to wander around the apartment, but also pointed out places for them to search. Defendant says he was forced to remain seated, but was not handcuffed until he was arrested.

The trial court and the Court of Appeals found that the defendant had validly assented to the police entry and search. Upon review of the evidence this Court reaches the same conclusion. There is sufficient evidence to support a holding that the police asked permission to enter and that consent was given to a general search. Further, just as the mere fact of custody without more, does not necessarily render consent involuntary, United States v Jordan, 399 F.2d 610, 614 (CA 2, 1968), the presence of a large number of officers in an apartment does not present a situation which is per se coercive.

The United States Supreme Court in Schneckloth implied that situations where Miranda warnings were required may still not be such as to invalidate consent to a search. The instant case is such a situation.

The trial court's and the Court of Appeals' holdings that consent was validly given to the search and that the evidence was correctly not suppressed were not clearly erroneous. We affirm.

VII — Conclusion

In view of our previous findings of error, we believe it unnecessary to reach defendant's other claims of error, most of which would not be necessarily pertinent to another trial in any event. However, the majority of this Court agree with defendant's objection to the introduction of the specified photographs of the nude dead bodies. People v Falkner, 389 Mich. 682; 209 N.W.2d 193 (1973).

The Court of Appeals and the trial court are reversed. We remand for new trial not inconsistent with this opinion.

T.G. KAVANAGH, C.J., and T.M. KAVANAGH, SWAINSON, LEVIN, and J.W. FITZGERALD, JJ., concurred with WILLIAMS, J.

M.S. COLEMAN, J., concurred in the result.