Page:Brief for the United States, Wong Sun v. United States, 371 U.S. 471 (1963).djvu/28

 To this may be added the further illumination of observations in the courts of appeals. In Christensen v. United States, 259 F. 2d 192, 193, the Court of Appeals for the District of Columbia Circuit said:

And in Bell v. United States, 254 F. 2d 82, 85 (C.A.D.C.), Judge Prettyman noted that suspicion on reasonable grounds is not the "mere suspicion" denounced in Mallory v. United States, 354 U.S. 449, 454, and stated (254 F. 2d at 85-86):

[Officers] do not schedule their steps in the calm of an office. Things just happen. They are required as a matter of duty to act as reasonably prudent men would act under the circumstances as those circumstances happen. * * *

[The] action [of an officer experienced in the narcotics traffic] is not measured by what might be probable cause to an untrained civilian passerby. When a peace officer makes the arrest, the standard means a reasonable, cautious and prudent peace officer. The question