Donald Kent Sanborn appeals from his conviction on a one count indictment charging armed robbery of $6,000 from the Milford Bank and Trust Company in Milford, Massachusetts on March 30, 1976 in violation of 18 U.S.C. § 2113(d).1

The Government's case was based largely on the testimony of an accomplice, Albert Kell, who, at the time of Sanborn's trial, had already been convicted of the robbery. There was evidence that Sanborn and Kell, both of whom had previously lived in Milford, planned the robbery during several February 1976 conversations in Pennsylvania. On March 29, 1976, Kell and Sanborn drove to Boston in Sanborn's car and checked into a motor inn. The next day, they left off Sanborn's car in Milford and picked up another which they drove to the bank. Shortly after the bank opened for business, Kell entered the bank, leaving Sanborn in the car. He went to the manager's office, took a gun from his attache case and demanded money. The manager turned over $6,000, Kell left the bank and escaped in the getaway car with Sanborn.

On appeal, Sanborn first argues that for him to be found guilty as an aider and abettor of armed as opposed to unarmed robbery,2 the Government must prove that he had knowledge that Kell would use a gun in robbing the bank and that the district court's failure to give a requested instruction precisely to that effect constituted reversible error.

Sanborn was convicted under the statute that makes an aider and abettor "punishable as a principal". 18 U.S.C. § 2. Appellant, citing to United States v. Short, 493 F.2d 1170 (9th Cir.), cert. denied, 419 U.S. 1000, 95 S. Ct. 317, 42 L. Ed. 2d 275 (1974), argues that an element of the Government's case was proof that he knew Kell planned to use a gun. Pointing to the lack of direct evidence that he knew of the gun Kell took the gun from an attache case after entering the bank Sanborn contends both that the Government did not make out a case of aggravated robbery against him and that denial of the requested instructions was fatal.

Sanborn is plainly wrong insofar as he argues that there was insufficient evidence from which to find that he knew of the gun.3 While there was no direct evidence, the circumstantial evidence permitted and, indeed, virtually compelled a conclusion of knowledge. Sanborn and Kell had carefully planned the robbery in advance, and were together for 8 or 9 hours on the previous day while driving from Pennsylvania to Massachusetts. Sanborn himself carried a gun when driving Kell to the bank where he waited for him until the two made their escape. A jury could reasonably conclude that an accomplice so closely associated with the venture could not fail to know what would be the central question in any robbery: how the robbers were to force the bank's employees to part with the money. Compare Pereira v. United States,347 U.S. 1, 12-13, 74 S. Ct. 358, 98 L. Ed. 435 (1954).

Not only was there ample evidence from which a jury could infer that Sanborn knew of Kell's use of a gun, but the court in its instructions emphasized that the Government had to establish Sanborn's intentional and wilful participation in the act of taking the money by intimidation, assault and jeopardizing the lives of employees. Since the evidence and instructions along these lines turned on Kell's use of the gun, the jury could scarcely have convicted without finding that Sanborn was aware of the gun. See id. at 9-10, 74 S. Ct. 358.

There remains nevertheless the question whether the court erred in declining Sanborn's requested instruction that his knowledge of the gun had to be proven. In United States v. Short, supra, 493 F.2d at 1172, the Ninth Circuit concluded that to convict one of aiding and abetting an armed robbery, the Government had to prove the accomplice's knowledge of the principal's use of the weapon as "an essential element" of the crime. To be sure, the district court in Short had instructed that the defendant could be convicted whether or not he knew a gun would be used; no such instruction was given here and, as already indicated, it is more than likely that the jury believed that Sanborn had knowledge. Still, if the accomplice's knowledge of the weapon forms part of the Government's burden of proof in establishing the aiding and abetting of an armed robbery, it would be error for the trial court not to so advise the jury upon request. We must, therefore, decide that question.

While there is little direct authority beyond Short, the modern case law tends to support the view that one charged as an aider and abettor of an aggravated robbery, requiring proof of use of a dangerous weapon, must be shown to have contemplated that a weapon would be used. See Commonwealth v. Ferguson, 365 Mass. 1, 8-9, 309 N.E.2d 182, 186-87 (1974); see also United States v. Methvin, 441 F.2d 584 (5th Cir. 1971). An aider and abettor need not know every last detail of the substantive offense, see Williams v. United States, 308 F.2d 664, 666 (9th Cir. 1962), but he must share in the principal's essential criminal intent. Johnson v. United States,195 F.2d 673, 675-76 (8th Cir. 1952); P. Anderson, Wharton's Criminal Law and Procedure § 114 at 247 (1957). While the § 2113(d) offense does not, in so many words, require the principal to be aware that he is using a dangerous weapon, his own knowledge is manifest from the fact of use, and in seeking to convict an aider and abettor of the aggravated offense we think the Government must show that the accomplice knew a dangerous weapon would be used or at least that he was on notice of the likelihood of its use. The accomplice's knowledge that use of a dangerous weapon was fairly within the robbery plan need not, of course, be shown by explicit proof of expressed intention; the jury may infer such knowledge from the whole circumstances. On this record, as already indicated, we would have no hesitancy whatever in affirming the present conviction for the aggravated crime had the court given an instruction that the Government had to establish beyond a reasonable doubt that Sanborn was on notice of the likelihood that a gun or other dangerous weapon would be used in the robbery. Absent any such instruction following upon defendant's explicit request,4 we are obliged to vacate the judgment of conviction for the aggravated § 2113(d) offense. Because the court's erroneous failure to instruct went only to the aggravated offense carrying a higher maximum sentence, and because we find no other error, so much of the judgment may stand as is a conviction of the lesser offense of robbery under § 2113(a). Alternatively, Sanborn may be retried for the aggravated offense.

We have considered all remaining arguments raised by appellant and find them to be without merit.

Upon the Government's filing of its election within one week, judgment will be entered.