HAMLIN, Circuit Judge.

Appellant was convicted on two counts of an indictment charging violations of 21 U.S.C. § 176a. On appeal he alleges error in that: (1) there was no probable cause for his arrest and consequently the evidence obtained in the search incident thereto was inadmissible; (2) the trial court abused its discretion in not granting his motion for a continuance; (3) the court committed prejudicial error in not granting his motion to discharge counsel; and (4) the evidence was insufficient to support his conviction.

The evidence, viewed — as it must be — in the light most favorable to the government, is set forth in the following paragraphs.

The United States Customs Service informed the Federal Narcotics Bureau that large amounts of marihuana were being smuggled into San Francisco and that it was believed that some of the marihuana would be used and concealed at 383A South Van Ness Avenue in San Francisco. Arrangements were made for a special employee of the Customs Service, Raoul Miller, to make a purchase of marihuana from one Elroy Jones (known to be a defendant in another narcotics case) at or near these premises on April 25, 1960. Federal narcotics agents, customs agents and officers of the San Francisco police department staked out the premises on this date.

At or about 7:20 p.m. appellant drove up in front of the premises and parked his car. Another car operated by one John Martinez arrived at the same time and was parked directly in front of appellant's car. Martinez and appellant got out of their cars, conferred briefly, and entered 383 South Van Ness; Martinez was carrying a large paper sack. Elroy Jones arrived at about 8:00 p.m. and also entered 383A. A few minutes later Jones came out of the premises and walked across the street to the corner of 15th and South Van Ness where he was joined by the special employee, Raoul Miller. They had a conversation lasting approximately one to one-and-a-half minutes. Jones then re-entered 383A and Miller walked slowly down South Van Ness Avenue to his car. At about 8:10 p.m. Jones came out of 383A carrying a package. He crossed the street, joined Miller and the two walked to Miller's car and entered it. Jones got out of the car after a very short time, Miller drove away, and Jones walked toward the corner of 14th and South Van Ness. Appellant came out of 383A with two small children and also proceeded toward the corner of 14th and South Van Ness where he was joined by Jones. They conversed and then walked back toward 383A. Appellant and the two children entered 383A and Jones continued on to his car and drove away.

After Miller had driven away following his meeting with Jones, he met a federal narcotics agent at the corner of Market and Van Ness and handed the agent a package of marihuana. The agent searched him and found that he did not have the $80 in marked money that had been given to him for the purpose of making the purchase. This information was radioed to the agents who were watching the premises at 383A South Van Ness. These agents then proceeded to the premises. An agent knocked on the door and announced in a loud voice: "Federal narcotics agents. Open the door, I want to talk to you." Upon receiving no response, the agent turned the doorknob and the door, which was unlocked, opened. The agents entered and placed appellant under arrest. Appellant was searched and the marked money was found on his person. One agent testified that appellant stated that he lived at the premises. The premises were searched and a quantity of marihuana was found in the bedroom. When asked where he got the marked money and the marihuana, appellant stated that he was holding the money and marihuana for a friend. An agent testified that later, at the office of the Bureau of Narcotics, appellant told him that the marihuana belonged to Martinez and had been left at his house to sell.

The marihuana which was the subject of the sale and the marihuana found at 383A South Van Ness, together with the four marked $20 bills found on appellant's person, were introduced into evidence at the trial. Although appellant now contends that his arrest was unlawful and that therefore the evidence obtained incident thereto was inadmissible, no motion to suppress the allegedly illegally obtained evidence, as required by Rule 41(e), Federal Rules of Criminal Procedure, was made before or during trial; nor was any objection raised by appellant when the evidence was admitted. Appellant, however, requests this court to consider his contentions under Rule 52(b).

Under Rule 52(b) we may in the exercise of our discretion notice plain errors affecting the substantial rights of a party though they were not brought to the attention of the trial court. We hold in the instant case that there was no error, let alone one affecting the substantial rights of appellant, in admitting the marihuana and marked money into evidence. The quantum or quality of evidence needed to show probable cause for an arrest is different from that required to sustain a conviction of a violation of the substantive offense. A federal narcotics agent may under 26 U.S.C. § 7607 make an arrest without a warrant if he has "reasonable grounds to believe that the person to be arrested has committed or is committing" a violation of a law of the United States relating to marihuana. Stated another way, it need only be shown in a particular case that the facts and circumstances within the arresting officer's knowledge and of which he has reasonably trustworthy information are "sufficient in themselves to warrant a man of reasonable caution in the belief that" an offense has been or is being committed. We have examined the evidence in this case, portions of which are summarized above, and believe that under the facts and circumstances of this case there was probable cause for appellant's arrest.

We shall next consider appellant's contentions that the trial court abused its discretion in not granting appellant's motion for a continuance and prejudicially erred in not granting his motion to discharge counsel.

At the conclusion of the government's case the court adjourned until the next day. On the next day, out of the presence of the jury, counsel for appellant moved for a continuance, stating that the government had failed to call Martinez and Jones as witnesses and that counsel would like to bring Martinez (who was in San Quentin) and Jones (whose whereabouts was unknown) into court to testify. The proceedings before the court, in the jury's absence, which followed are set forth in the margin.

We hold that the district court did not abuse its discretion in denying appellant's motion for a continuance for the purpose of producing Martinez and Jones at the trial. Neither Martinez nor Jones was required by the government to prove its case and thus there was no reason for the government to call them as witnesses. Since there was no showing as to the nature and materiality of the expected testimony of Martinez and Jones, the district court's refusal to grant the continuance was in accordance with the provisions of Rule 13(b), Rules of Practice, United States District Court. Northern District of California.

The question remains whether the district court committed prejudicial error in denying appellant's motion to dismiss his counsel. Under 28 U.S.C. § 1654, "parties may plead and conduct their own cases personally" in courts of the United States. It would seem clear under this provision that a party who intelligently and competently waives the right to counsel prior to the commencement of trial should be allowed to conduct his own defense and this court has so held.

If the defendant requests to conduct his own defense after the trial has begun, the trial judge is faced with a more difficult situation. First of all, he must, as in any case, determine whether, based upon the facts and circumstances of the case, including the background, experience and conduct of the accused, the request was intelligently made. We feel that based upon the facts and circumstances of this case the district court could reasonably conclude that appellant had not made an intelligent waiver of his right to counsel. The only reason given by appellant for his desire to discharge counsel was that he (appellant) wanted to bring Martinez and Jones into court to testify and yet the court had repeatedly told him that he could not have a continuance for that purpose. When asked how he would proceed, he could only say that he wanted these witnesses. We submit that under these circumstances had the district court discharged his counsel at that stage in the proceedings, appellant would be before this court today urging that he had not intelligently waived his right to counsel.

Further, the orderly conduct of a jury trial is the responsibility of the trial judge. It is clear, for example, that an accused does not have an absolute right to change attorneys during the course of a trial. In United States v. Mitchell, 137 F.2d 1006, 2 Cir., the Court of Appeals for the Second Circuit stated:

"The cases cited by defendant stress equally, as, indeed, they properly should, the right of an accused to act for himself and his right to have a lawyer assigned in his behalf. [Citations] Obviously, however, those rights cannot be both exercised at the same time. The cases are dealing with a choice to be made at the opening of the trial. It would be unfair to say no further choice is possible after the case is opened, but it would be just as unfair to say that when a defendant sees a strong case made against him he can immediately dismiss assigned counsel and then obtain a delay — and often a mistrial, at least in districts where calendars are crowded — through the device of having new counsel assigned to him."

If the defendant does not request a change of counsel, but rather requests to conduct his own defense, it would seem that the trial court should have discretion to refuse the request if made only after a strong case has been presented against the accused and if from the circumstances it appears to be motivated by a desire to disrupt the orderly conduct of the trial. Thus, in United States v. Foster, 9 F.R.D. 367 (S.D.N.Y. 1949) Judge Medina in refusing to allow a defendant to proceed in pro se stated:

"Thus, at the outset, it seems significant that neither the Constitution nor the applicable federal statute lend the slightest support to the claim that Mr. Davis may dismiss his counsel, and sum up in his own behalf, as matter of right. The clear purport of the language just quoted seems to the contrary. One of the fundamental rights of defendants in criminal cases is the right to counsel. But the alleged absolute right, irrespective of the attendant circumstances, to dismiss counsel and carry on pro se is a quite different proposition. If such were the law, there would be fertile field in which defendants in criminal cases could operate to frustrate justice and, under the aegis of an alleged constitutional or other right, resort to every bedevilment of the court and jury that the ingenuity of man could devise."

In the instant case appellant attempted to discharge his counsel after a strong case had been presented against him. There had been no indication prior to his request that he was in any way dissatisfied with the services of his counsel; nor was he able at the time of his request to give any convincing reason for his desire to discharge his counsel. Under the circumstances, it would be reasonable for the trial court to conclude that appellant's request was actuated by a desire to disrupt the orderly proceeding of the trial. After the refusal of his request, he took the witness stand and under the tutelage of his counsel presented his defense. At the conclusion of the case, his counsel presented an able argument in his behalf to the jury. We hold that under the circumstances of this case, the district court did not err in refusing to allow appellant to conduct his own defense.

It is clear that there was sufficient evidence to support appellant's conviction and therefore the judgment is affirmed.

* * * * *

* * * * *