Rosellini, J.
The appellants Todd and Stewart were charged as principals and the appellant Wood as an aider and abetter in the crime of murder in the first degree. All were found guilty.
None of the appellants questions the sufficiency of the evidence to support the convictions. That evidence tended to show that the appellants met at a party in Seattle’s central area on the evening of May 28, 1967; that during the course of the evening the appellant Wood loaned his car and his gun to the other two appellants for the purpose of committing a robbery; that the appellants Todd and Stewart did in fact participate together in the robbery of a Seattle Transit bus being operated by one Harry Lee Wren, [364]*364Jr., and that, during the commission of this robbery, Harry Lee Wren, Jr., was slain. Todd and Stewart returned to the party and thereafter, together with appellant Wood, disposed of the stolen property.
The appellants and another man went to Portland, Oregon, and participated in another robbery the following afternoon. As a result of the description of this offense being broadcast on police radios, the appellants were apprehended a few minutes later. In their possession was found not only the goods which were stolen in the Portland robbery but also the gun which, according to a firearms identification expert’s testimony, fired the shot which killed Harry Lee Wren, Jr.; also there were found women’s stockings which the appellants Todd and Stewart had borrowed at the party to use as masks in the Seattle robbery and which had been cut and tied with the apparent object of using them as masks.
The evidence against the appellants was supplied in large part by other guests at the party, to two of whom the appellant Todd stated that he had had to “blast” the driver of the bus because he would not open the door of the bus and let him get off. One of these witnesses, the girl friend of Todd, later led police to the spot where the coin changer taken from the bus had been thrown by appellant Stewart, while the witness was riding in the car with the appellants after the robbery.
The three appellants were charged jointly and they were tried together. Their separate appeals to this court were consolidated for hearing. All three appellants have urged one assignment of error relating to the admission of certain evidence, and the appellants Stewart and Wood have both urged that their motions for severance should have been granted. Each of the remaining assignments of error has been advanced by one of the appellants. We will discuss the contention concerning the admissibility of evidence alleged to have been discovered in an unlawful search first, the contentions of the appellants Stewart and Wood concerning severance second, the separate contentions of the appellants Stewart and Wood next, and finally we will consider the [365]*365only contention having merit, that of the appellant Todd concerning an allegedly erroneous instruction.
The contention that certain evidence (namely the gun which was used to kill Harry Lee Wren, Jr., and ammunition for it, and two women’s stockings which were supposedly used as masks in the robbery) was erroneously admitted is grounded on the theory that Deputy Sheriff Hancock, who stopped the appellants’ automobile in Portland, had no legitimate reason to stop it because, they say, they were driving in a lawful manner at the time they were stopped, and the officer did not have probable cause to believe that they had committed or were about to commit a felony.
In order to be justified in arresting without a warrant, an officer must believe and must have good reason to believe that a person has committed or is about to commit or is in the act of committing a felony. Not only must the officer have a real belief that the person is guilty, but that belief must be based upon reasonable grounds. Proper cause for arrest has often been defined to be a reasonable ground of suspicion, supported by circumstances sufficiently strong in themselves to warrant a cautious man in believing the accused to be guilty. State v. Palmer, 73 Wn.2d 462, 438 P.2d 876 (1968); State v. Easton, 69 Wn.2d 965, 422 P.2d 7 (1966); State v. Miller, 151 Wash. 114, 275 P.75 (1929).
The trial judge in this case concluded that Deputy Sheriff Hancock had reasonable and probable cause to 'arrest the appellants. He based his conclusion upon the following facts which he found upon the evidence and which are supported by it: Multnomah County Deputy Sheriff Hancock had received a radio message that a robbery had been committed at a grocery store between 52nd and 53rd Streets on Halsey Street in the city of Portland. The suspects were described as being three Negroes of slight build, and as having departed the scene in an automobile. Deputy Sheriff Hancock knew that Halsey Street was a logical eastbound thoroughfare for departure from the city of Portland and assumed a position of surveillance near Halsey and 92nd. At approximately the time which he calcu[366]*366lated a vehicle coming from 52nd would be passing the point where he was stationed, the appellants were observed in an automobile proceeding east along Halsey Street.
While the automobile did not conform to the description given over the radio, there were three Negro men of slight build visible in the car; and the officer stopped the car, believing that the three were the people who had committed the robbery. He explained that he noted the car did not conform to the description but supposed the car had either been misdescribed or had been exchanged for another car after the robbers left the scene of the robbery.
The appellants say that Deputy Sheriff Hancock would have stopped any vehicle with three Negro men in it which might have been passing at that time, even though the occupants were entirely innocent. This proposition is not justified by the evidence in this case. The fleeing felons were described not only as Negroes but also as slender or slight of build and the appellants fitted that description. The officer was justified in believing that the appellants were the persons who committed the robbery.
If the robbers had been described as three white men of slight build, and three white men of that description had driven past the same spot at the same time and proceeding in the same direction, the officer would have had probable cause to arrest them. Of course, if only one man had been involved, the description would have been inadequate to justify an arrest, since it would not be unusual for more than one person of that description to drive past a given point within a short period of time. But it would have been coincidental indeed if another vehicle bearing three men of the same description had passed that point at that particular time, headed in the same direction. Deputy Sheriff Hancock’s experience had taught him that escape vehicles are sometimes misdescribed because only a fleeting glimpse is caught of them. It had also taught him that fleeing felons often change vehicles. Therefore, it was not unreasonable for him to discount the fact that the vehicle did not fit the description broadcast over his car radio.
[367]*367The appellants make much of the fact that there were four men in the vehicle, rather than three, but the evidence showed that one of them was lying on the back seat of the car and was not visible to the officer. Apparently he was not observed at the scene of the crime, since the participants were described as three, rather than four men.
In State v. Young, 39 Wn.2d 910, 917-18, 239 P.2d 858 (1952), we said:
It is the duty of courts to protect citizens from unwarranted, arbitrary, illegal arrests by officers of the law. But we should not permit our zeal for protection of constitutional rights to blind us to our responsibility to other citizens who have the right to be protected from those who violate the law. In these days of modern transportation, when robbers have fast “get-away” cars, police must also have fast cars. Those fast cars must be equipped with radios, in order that law violators may be apprehended before they can make their escape, provided of course, that the officers have reasonable grounds to believe that the persons whom they arrest have committed the felony complained of.
And in State v. Poe, 74 Wn.2d 425, 445 P.2d 196 (1968), we observed that the probable cause for arrest should be examined in the light of the arresting officer’s special experience, and that the standard should be, not what might appear to be probable cause to a passerby, but what would be probable cause to a reasonable, cautious, and prudent officer.
Here the officer anticipated that the escaping felons would choose the route on which he stationed his vehicle; at a time when an automobile coming from the scene of the crime could be expected to reach the place where the officer was stationed, the appellants, whose physical appearance matched the description given over the police radio, drove past headed away from the scene of the crime. He noted that the car did not match the description, but did not consider this significant in the light of his knowledge and experience. He had only a moment to make a judgment, but the judgment which he made was sound.
We conclude that there was probable cause for arrest. [368]*368Consequently, the fruit of the search made incident to that arrest was admissible.
In assigning error to the court’s denial of their motions for separate trials, the appellants Stewart and Wood concede that the granting of such a motion rests within the sound discretion of the trial court. However, they call the court’s attention to the case of Bruton v. United States, 391 U.S. 123, 20 L. Ed. 2d 476, 88 S. Ct. 1620 (1968), wherein the United States Supreme Court held that, in a joint trial, admission of a codefendant’s confession implicating the defendant violated his right of cross-examination of the witnesses against him because of the substantial risk that the jury, despite instructions to the contrary, looked to the incriminating extrajudicial statements in determining the petitioner’s guilt. They suggest that the corollary of the rule laid down in that case (that such a confession is not admissible in a joint trial) is that it is an abuse of discretion to deny a motion for severance in any case where statements of one defendant incriminating another may be possibly offered in evidence at the trial.
We say that this is the suggested corollary because it is not so stated in the brief; but there is no contention that any such statements were in fact offered in this trial. As a matter of fact, there were no extrajudicial confessions implicating either of these appellants. It is true that Todd had made statements to friends shortly after the crime was committed; these implicated only himself. Each appellant denied his guilt to investigating officers and to the court, both before and during the trial. Statements made by each to the police may have implicated the others in his alibi, but not in the crime.
In State v. Aiken, 75 Wn.2d 421, 452 P.2d 232 (1969), we held that the case of Bruton v. United States, supra, did not stand for the proposition that, where both defendants have confessed and each confession has implicated the other, and where there is other circumstantial evidence tending to prove the guilt of the defendants beyond a reasonable doubt, separate trials must nevertheless be granted. As we observed, in Bruton the United States Supreme Court was [369]*369confronted with a case where one of the codefendants had made a confession and the other had not, where the confession implicated the nonconfessing defendant and was the only substantial evidence against him, and where the conviction of the confessor was itself set aside on appeal because his confession was involuntary.
That situation bears no resemblance to the situation presented to the trial court in this case. Here the prosecutor revealed that he had no confessions to offer in evidence and furthermore pointed out to the court that if, during the course of the trial, he should offer any extrajudicial statements of any defendant which might be prejudicial to another defendant, the court could exclude it. Apparently in the course of the trial, the only statement offered which was conceivably inadmissible against either Stewart or Wood was a statement attributed to Wood, made at the party, that he had lent his car to Todd and Stewart. The court instructed the jury that it should consider this as evidence only against the appellant Wood. It has not been argued by the prosecution that the court was in error in so limiting the probative value of this evidence, so we do not consider that question. Suffice it to say that the statement was not a confession, and standing alone it proved little as to the guilt of Stewart. It may have been corroborative, but the guilt of Stewart and Todd was shown by other independent and convincing evidence. Whether or not the court’s instruction to consider the evidence only as evidence against Wood was understood and followed by the jury, the significance of the evidence was so slight that, when viewed in the light of all the other evidence, the appellant Stewart could not have been prejudiced by it.
We conclude that the rule of the Bruton case did not require the trial court to grant the appellants’ motions for separate trials.
Some additional argument is made that the appellants’ defenses were incompatible, but it is not shown wherein that alleged incompatibility lay. All of the appellants denied any involvement in the crime; none tried to implicate the others. This contention is without substance.
[370]*370We find no abuse of discretion on the part of the trial court in denying the motion for severance.
Turning now to the separate contentions of the appellants, we consider first those of the appellant Stewart. He assigns error to the court’s refusal of his requested instruction pertaining to his defense of alibi. This instruction stated that, if a person is charged with having been present and having participated in the commission of a crime and if in fact he was not present, his absence is a complete defense called “alibi.” It further stated that Stewart had introduced evidence tending to prove that he was not present at the murder and that, if the jury entertained a reasonable doubt whether or not he was present, it should 'acquit him.
The trial court correctly refused this proposed instruction. While the appellant Stewart was charged as a principal, the prosecution was entitled to ask for a verdict of guilty even though the evidence showed only that he had aided and abetted the commission of the crime. State v. Olson, 50 Wn.2d 640, 314 P.2d 465 (1957); State v. Cooper, 26 Wn.2d 405, 174 P.2d 545 (1946). The trial court instructed the jury:
No. 10
Under the statutes of the State of Washington every person who stands by aiding, assisting, or abetting, or who, not being present, directly or indirectly, has aided, assisted, abetted, advised, encouraged, or counseled the perpetration of a crime is guilty of the commission of the crime and shall be proceeded against and punished as a principal.
The words “aid and abet” comprehend all assistance rendered by words, acts, encouragement, support of presence, actual or constructive, to render assistance should it become necessary.
No exception was taken to this instruction by the appellant Stewart. Under its language, the jury was entitled to find that the appellant was guilty even though he was not present at the time of the actual shooting. The requested instruction concerning “alibi” was contrary to the law applicable to the case. The jury might well have found that the state had failed to prove that the appellant boarded the [371]*371bus with the appellant Todd, and still have found that he aided and abetted him in the commission of the crime. The instruction advised to the contrary and was therefore improper.
The remaining contention of the appellant Stewart is that the court erred in refusing to dismiss the case against him because he was not given a preliminary hearing. The same contention was considered by this court in State v. Kanistanaux, 68 Wn.2d 652, 414 P.2d 784 (1966), wherein we held that a defendant has no right to such a hearing, and that the prosecutor may elect to charge a defendant directly in superior court, bypassing the preliminary hearing in justice court. That decision was reaffirmed by State v. Smith, 74 Wn.2d 744, 446 P.2d 571 (1968). The appellant has shown no reason why that decision was erroneous nor has he made any showing that he was in any way prejudiced by the lack of such a hearing. This contention is likewise without merit.
The appellant Wood assigns error to the admission of evidence that the appellant Todd held a pistol in his hand on the night of his arrest in Portland, Oregon, claiming that it was evidence of another unrelated crime and prejudicial to the appellant Wood, since Wood was with appellant Todd in Portland.
Assuming that the appellant is correct that this evidence tended to prove the commission of another crime, it was nevertheless clearly relevant in connecting Todd with the crime charged, the gun having been shown to have been the one which was used in the Seattle murder of Harry Lee Wren, Jr. Relevant evidence is not inadmissible simply because it tends to prove another offense. State v. Mott, 74 Wn.2d 804, 447 P.2d 85 (1968).
The other separate contention of Wood is that the trial court committed error in permitting the prosecution to question him on cross-examination about seeing the gun, the stockings, and the other items in the car in Portland. The respondent points out that the appellant Wood voluntarily took the stand and on direct examination testified that, contrary to the testimony of witnesses who had said [372]*372he had brought the gun to the party on the night of the killing and had given it to Todd and Stewart to use. in the commission of a robbery, he had not brought the gun to the party. The questions regarding his seeing the gun in the car in which he was riding in Portland were designed to test the credibility of this statement. (See State v. Robideau, 70 Wn.2d 994, 425 P.2d 880 (1967).) But even assuming that some of the questions asked exceeded the scope of the direct examination, the appellant has failed to point out how he was prejudiced by the asking and the answering of these questions.
The fact that a gun belonging to the appellant Wood, ammunition, and women’s cut-off stockings were found in the car in which the appellant Wood was arrested in Portland had been placed before the jury in other competent testimony. The jury was entitled to weigh this evidence and the additional evidence before it that the gun was the weapon used in the murder, against Wood’s statement that he did not take the gun to the party. The appellant Wood has not drawn our attention to any fact brought out on cross-examination which was not already before the jury. The admission of evidence which is merely cumulative is not prejudicial error. State v. Swanson, 73 Wn.2d 698, 440 P.2d 492 (1968).
Having disposed of those contentions which we have found to be without merit, we reach a question raised by the appellant Todd which concerns only the sentence of death imposed upon him by the verdict of the jury. The appellants Stewart and Wood were spared the death penalty and, consequently, the instruction complained of by the appellant Todd had no adverse effect upon the jury’s verdict against them.
The appellant Todd took exception to the giving of the following instruction:
No. 12
In the event you find a defendant guilty of the crime of murder in the first degree, and you do not direct the imposition of the death penalty, the court must then sentence the defendant to imprisonment for life.
[373]*373Under the laws of this state, any person, including a person sentenced to imprisonment for life, is eligible to be paroled. Any prisoner on any life sentence will have a minimum sentence set for him by the Board of Prison Terms and Paroles. This minimum sentence cannot be reviewed or revised by any court unless the Board of Prison Terms and Paroles acts beyond their authority.
On a sentence of life imprisonment, the Board of Prison Terms and Paroles must set a minimum sentence of at least twenty years, and may set the minimum in any amount of time in excess of twenty years as in their discretion and judgment they deem proper.
Any prisoner may earn credit for time off their minimum sentence for good behavior. This credit may be as much as one third of their minimum sentence. Therefore, it is possible for a person serving a life sentence for murder in the first degree to be eligible for parole in thirteen and two-thirds years.
The trial court refused to omit the instruction, being of the opinion that it was authorized by language contained in the case of State v. Collins, 50 Wn.2d 740, 314 P.2d 660 (1957). The trial court also took notice of the fact that counsel for the appellants had asked prospective jurors on voir dire, “Could you vote for life imprisonment as opposed to the death penalty?”
It is the position of the appellant Todd that this court has never actually approved the giving of an instruction like instruction No. 12, that it is misleading, and that it permits the prosecutor to argue to the jury that, if it does not impose the death penalty, the accused may well be on the streets again in 13% years, when in fact it is extremely improbable that the appellant in this case would be paroled in such a short period of time. Furthermore, he argues, the instruction permits the jury to speculate upon matters which it is not within its province to consider and which have been assigned by the legislature to the exclusive jurisdiction of the parole board.
The respondent answers that the appellant Todd has opened up the question for speculation on the part of the jury by asking the jurors on voir dire whether or not they could “vote for life imprisonment.” While arguing that the [374]*374appellant has planted in their minds the idea that “life imprisonment” means imprisonment without parole, he also argues on the other hand that the instruction is beneficial to the appellant because without it the jurors would speculate that a man condemned to life imprisonment could be released in 1 year.
Contrary to the understanding of the trial court and of the respondent, this court did not approve the giving of such an instruction in State v. Collins, supra. In that case, the trial court instructed the jury that, if it found the defendant guilty of murder in the first degree, it should determine further whether the death penalty should be imposed. The defendant urged on appeal that the trial court should have instructed the jury that, if it did not impose the death penalty, a life sentence was mandatory.
We held that the trial court did not err in refusing to give this instruction and remarked that such an instruction without an explanation of the powers and functions of the parole board would be misleading. This, of course, was one reason why the requested instruction was properly refused, but we did not intend to suggest that the giving of an instruction which outlined those powers and functions, over the objection of the defendant, would be proper.
The statute providing for the imposition of the death penalty, RCW 9.48.030, in pertinent part, reads as follows:
[I]n every trial for murder in the first degree, the jury shall, if it find the defendant guilty, also find a special verdict as to whether or not the death penalty shall be inflicted; and if such special verdict is in the affirmative, the penalty shall be death, otherwise, it shall be as herein provided.
The statute thus provides that the jury shall decide “whether or not the death penalty shall be inflicted.” It does not provide that the jury shall choose between penalties, but only that it shall decide whether to take the defendant’s life or spare it. This may seem, at first glance, rather a nice point; but when it is considered that the alternative is not in fact a single possibility but as many possibilities as there are years left in the defendant’s life, [375]*375that the determination of the duration of the sentence is placed ultimately in the hands of the parole board, that one of the aims of punishment is rehabilitation and that rehabilitation is not thought hopeless, it is not so unreasonable to suppose that the legislature did indeed intend the jury to decide the one stark question, shall this man’s life be spared? unaided by any basis of speculation as to what his future might hold if it should decide in favor of mercy.
It must be remembered that, in all other prosecutions, the jury is told that punishment is none of its concern, that its sole function is to decide the defendant’s guilt or innocence. Punishment is a question of legislative policy; the jury’s function is to find the facts.
But when it comes to the imposition of the death penalty, the legislature has seen fit to make that question hinge upon a further fact to be found by the jury — how deeply has the defendant offended the community? As we have recognized in State v. Smith, 74 Wn.2d 744, 774, 446 P.2d 571 (1968), the legislature has provided no standards. We held there that this failure does not constitute a denial of equal protection of the laws or of due process of law. We observed in that case:
As we said in State v. Aiken, 72 Wn.2d 306, 434 P.2d 10 (1967), the viciousness and callousness of the killings are matters which the jury necessarily considers in determining whether to impose the death sentence. Circumstances mitigating against it, if shown by the evidence, are also to be considered. The jury does not need express instructions that it should consider these matters. They are all a part of the evidence, and properly considered by the jury in reaching its decision.
The appellant Todd has cited a number of cases from other jurisdictions in which courts have held that the giving of an instruction such as instruction No. 12 is prejudicial error, because it allows the jury to speculate upon a matter which it is not within its province to consider, that is, the possibility of parole. These include In re Pike, 66 Cal. 2d 170, 424 P.2d 724, 57 Cal. Rptr. 172 (1967); People v. Morse, 60 Cal. 2d 631, 388 P.2d 33, 36 Cal. Rptr. 201 (1964); Burnette v. State, 151 So. 2d 9 (Fla. 1963); Sukle v. [376]*376People, 107 Colo. 269, 111 P.2d 233 (1941); Williams v. State, 191 Tenn. 456, 234 S.W.2d 993 (1950).
In some jurisdictions, it has been held proper for a jury to consider the possibility of parole so long as the trial court specifically states that this subject is not a matter for consideration and speculation by the jury. Lee v. State, 265 Ala. 623, 93 So. 2d 757 (1957); State v. Conner, 241 N.C. 468, 85 S.E.2d 584 (1955); State v. White, 27 NJ. 158, 142 A.2d 65 (1958); and Liska v. State, 115 Ohio St. 283, 152 N.E.667 (1926).
In spite of all of these authorities to the effect that a jury should not consider the possibility of parole, it is conceded by counsel for both sides on this appeal that juries inevitably do consider these possibilities. The respondent argues that the jury, since it will speculate in spite of all instructions not to do so, should be given the facts so that it can have some basis for its speculations. Appellant Todd, on the other hand, urges that the instruction merely gives the prosecutor the benefit of a judicial pronouncement upon the authority of which he can argue to the jury that the appellant will be paroled in the minimum length of time if he is not hanged. He also argues, and quite persuasively, that the instruction (which merely cites the possibilities) does not give the jury the “facts” — that the facts include the practices of the parole board, the average minimum sentence, the incidence of recidivism, the prospects of rehabilitation, and other factors which influence the parole board in the exercise of its powers.
This argument of appellant Todd leads us to what we consider the most serious vice of an instruction of this kind. It sets a standard where none has been set by the legislature and thus places undue emphasis upon one factor which the jury, whether or not it should do so, is bound to take into account. All other factors come before the jury in the form of evidence or of their own experience and knowledge. By instructing the jury concerning the possible minimum sentence which the defendant might serve, the court suggests to the jury that it should give great weight to that possibility in reaching its verdict.
[377]*377In this case, a surmisal that the jury did give considerable weight to that factor is supported by a showing in the record that the jury sent a note to the judge recommending that the highest possible terms be set for the other two appellants. Perhaps there is slight probability of prejudice in this case, where the evidence of guilt was overwhelming and the callousness manifest; still, when the death penalty is involved, every doubt should be resolved against the state and in favor of the defendant. For this reason, we are of the opinion that it was prejudicial error to give this instruction over the objection of the appellant.
We must necessarily observe that not every defendant considers the instruction prejudicial. In the case of State v. Smith, supra, the defendants did not object to the instruction, but simply contended that the court should have instructed, in addition, that the parole board is presumed to do its duty, a concept which, in our opinion, was implicit in the instruction given. In that case, any error in giving the instruction was waived.
Since the single error occurring at the trial concerned only the verdict as to the punishment of appellant Todd and not as to the guilt of any of the appellants, a new trial on the issue of guilt is unnecessary. While we have no statutory provision for a bifurcated trial as such, the legislature has sanctioned a trial to determine the degree of the crime and the punishment, where a defendant pleads guilty to murder, in RCW 10.49.010. Here the guilt and the degree of the crime have been determined in a trial free of error affecting those determinations. The legislature in that statute implicitly recognized that, in a proper case, there may be a jury trial on the issue of punishment alone. In its present posture, this is such a case.
The judgments as to the appellants Stewart and Wood are affirmed. The judgment as to the appellant Todd is affirmed on the issue of guilt, but the sentence is set aside and the cause is remanded for a new trial on- the issue of punishment.
[378]*378Hunter, C. J., Hamilton, Neill, and McGovern, JJ., concur.