What is the test for warrantless arrest for possession of child pornography?

^20.Cf. United States v. Hill, 459 F.3d 966, 972-73 & n.9 (9th Cir. 2006) (while a single photo of a naked child in a bathtub would not suffice to establish probable cause for a search warrant, a detailed description of two photographs of semi-nude girls revealing their breasts and pubic areas, which could have been meant to " 'arouse or satisfy the sexual cravings of a voyeur,' " produced probable cause to believe that evidence of child pornography would be found on the defendant's computer, even if the defendant could negate their contraband nature at trial (quoting United States v. Wiegand, 812 F.2d 1239, 1244 (9th Cir. 1987))); United States v. Moore, 215 F.3d 681, 686-87 (7th Cir. 2000) (finding that photos of nude children, including some depicting nude boys in nature scenes that were not necessarily sexually suggestive and some depicting nude girls in sexually suggestive poses, produced probable cause to effect a warrantless arrest for possession of child pornography).