On a motion to suppress evidence on the grounds of a warrantless arrest, "the burden is on the Government to show that there was probable cause for the arrest." United States v. Rivera, 321 F.2d 704, 706 n.1 (2d Cir. 1963). Obviously, however, the moving party must make a preliminary showing as to the circumstances of the arrest sufficient to raise a question as to its legality.

After an arrest without a warrant is made, a complaint has to be filed and probable cause must be established in the complaint or by way of accompanying affidavits or affirmations. Fed.R.Cr.P. 5(a). The party moving for suppression of statements based on an arrest allegedly made in the absence of probable cause must make a preliminary showing concerning the circumstances of the arrest sufficient to raise a question as to its legality. See United States v. Rivera, 321 F.2d 704, 706 n. 1 (2d Cir. 1963). The government, however, has the burden of showing that probable cause existed at the time of the arrest.

Thus the sole issue is whether at the time of the arrest, made without a warrant, the arresting agents had reasonable grounds for believing that defendant Soyka had committed or was committing a violation of the narcotics laws. Rios v. United States, 364 U.S. 253, 80 S.Ct. 1431, 4 L.Ed.2d 1688 (1960); Johnson v. United States, 333 U.S. 10, 68 S.Ct. 367, 92 L.Ed. 436 (1948); United States v. Rivera, 321 F.2d 704 (2d Cir. 1963); 26 U.S.C. § 7607. There is no doubt that "[t]he quantum of information which constitutes probable cause * * * must be measured by the facts of the particular case."

A court must ordinarily hold "[a]n evidentiary hearing on a motion to suppress . . . if 'the moving papers are sufficiently definite, specific, detailed, and nonconjectural to enable the court to conclude that contested issues of fact going to the validity of the search are in question." United States v. Pena, 961 F.2d 333, 339 (2d Cir. 1992) (quoting United States v. Licavoli, 604 F.2d 613, 621 (9th Cir. 1979)); see also In re Terrorist Bombings of U.S. Embassies in E. Afr., 552 F.3d 157, 165 (2d Cir. 2008); United States v. Rivera, 321 F.2d 704 n.1 (2d Cir. 1963) ("Obviously . . . the moving party must make a preliminary showing as to the circumstances of [an alleged Fourth Amendment violation] sufficient to raise a question as to its legality."). Because Durand sufficiently demonstrated to the district court that the postal inspectors were investigating the mail and identity fraud crimes for months and that the inspectors knew before his interview a small number of phone numbers were critical to their investigation (as one inspector would later state in an affidavit, the inspectors were aware that such phone numbers have significant investigative value in identity fraud cases), Durand at least alleged a sufficient basis to raise the evidentiary issue of whether the inspectors' questions about his phone number were reasonably likely to elicit incriminating information, and thus violated the Fifth Amendment.

A court must ordinarily hold "[a]n evidentiary hearing on a motion to suppress . . . if 'the moving papers are sufficiently definite, specific, detailed, and nonconjectural to enable the court to conclude that contested issues of fact going to the validity of the search are in question." United States v. Pena, 961 F.2d 333, 339 (2d Cir. 1992) (quoting United States v. Licavoli, 604 F.2d 613, 621 (9th Cir. 1979)); see also In re Terrorist Bombings of U.S. Embassies in E. Afr., 552 F.3d 157, 165 (2d Cir. 2008); United States v. Rivera, 321 F.2d 704 n.1 (2d Cir. 1963) ("Obviously . . . the moving party must make a preliminary showing as to the circumstances of [an alleged Fourth Amendment violation] sufficient to raise a question as to its legality."). Because Durand sufficiently demonstrated to the district court that the postal inspectors were investigating the mail and identity fraud crimes for months and that the inspectors knew before his interview a small number of phone numbers were critical to their investigation (as one inspector would later state in an affidavit, the inspectors were aware that such phone numbers have significant investigative value in identity fraud cases), Durand at least alleged a sufficient basis to raise the evidentiary issue of whether the inspectors' questions about his phone number were reasonably likely to elicit incriminating information, and thus violated the Fifth Amendment.

But the question of how far, if at all, the moving defendant must go beyond showing that the arrest was without a warrant is not without its difficulties.United States v. Rivera, 321 F.2d 704, 706 n. 1 (2d Cir. 1963). In addition, "[a]n evidentiary hearing on a motion to suppress ordinarily is required if `the moving papers are sufficiently definite, specific, detailed, and nonconjectural to enable the court to conclude that contested issues of fact going to the validity of the search are in question.'"

[emphasis added] See also Beck v. Ohio, 379 U.S. 89, 91, 85 S.Ct. 223, 13 L.Ed.2d 142 (1964); Carroll v. United States, 267 U.S. 132, 162, 45 S.Ct. 280, 69 L.Ed. 543 (1925); U.S. v. Tramontana, 460 F.2d 464, 467 (2nd Cir. 1972), and United States v. Rivera, 321 F.2d 704, 708 (2nd Cir. 1963). United States v. Rivera, supra, at 707 states:

And in Henry v. United States, 361 U.S. 98, 80 S.Ct. 168, 4 L.Ed.2d 134 (1959), the information known to the officers was far less than here. Much more analogous are such decisions as United States v. Elgisser, 334 F.2d 103, 111 (2d Cir.) (concurring opinions of Lumbard, C.J., and Friendly, J.), cert. denied, Gladstein v. United States, 379 U.S. 879, 85 S.Ct. 148, 13 L.Ed.2d 86; 379 U.S. 881, 85 S.Ct. 151, 13 L.Ed.2d 87 (1964), United States v. Rivera, 321 F.2d 704 (2d Cir. 1963), and United States ex rel. Wilson v. LaVallee, 367 F.2d 351 (2d Cir. 1966), in which arrests without warrants were held proper. Cf. Gilbert v. United States, 366 F.2d 923, 931 (9th Cir. 1966), cert. denied, 388 U.S. 922, 87 S.Ct. 2123, 18 L.Ed.2d 1370 (1967).

The burden of proof has been well stated as follows: "It is clear that in every case the government has the burden of establishing that the probable cause requirement has been met, Wong Sun v. United States, 371 U.S. 471, 479-480, 83 S.Ct. 407, 9 L.Ed.2d 441 (1963); Carroll v. United States, supra [ 267 U.S. 132, 45 S.Ct. 280, 69 L.Ed. 543]; United States v. Rivera, 321 F.2d 704, 708, 2 Cir. 1963; United States v. Dornblut, 261 F.2d 949, 2 Cir. 1958. The government, however, may not validate an initially invalid arrest by the fruits of the incidental search.

But by the time of the entry, corroboration was supplied by Riley's emergence from 146-12 with bootleg whiskey and by the heat and smell of mash. See United States v. Rivera, 321 F.2d 704, 708-709 (2d Cir. 1963); United States v. Smith, 308 F.2d 657, 662-663 (2d Cir. 1962) (Waterman, J.), cert. denied, 372 U.S. 906, 83 S.Ct. 717, 9 L.Ed.2d 716 (1963). As with the informer, see note 4 supra, Riley's reliability was corroborated by the agents' own observations of him that evening, and the suggestion that, although he need say nothing, he should not lie. This, and the greater specificity of the guidance given to the officers, serve to distinguish Riley's information from that given by Hom Way in Wong Sun.