Page:Riley v. California Opinion.djvu/12

 Opinion of the Court exigent circumstances. See, e.g., Warden, Md. Penitentiary V. Hayden, 387 U. S. 294, 298-299 (1967) ("The Fourth Amendment does not require police officers to delay in the course of an investigation if to do so would gravely endanger their lives or the lives of others."). 2 The United States and California focus primarily on the second Chimel rationale: preventing the destruction of evidence. Both Riley and Wurie concede that officers could have seized and secured their cell phones to prevent destruction of evidence while seeking a warrant. See Brief for Petitioner in No. 13-132, p. 20; Brief for Respondent in No. 13-212, p. 41. That is a sensible concession. See Illinois v. McArthur, 531 U. S. 326, 331-333 (2001); Chadwick, supra, at 13, and n. 8. And once law enforcement officers have secured a cell phone, there is no longer any risk that the arrestee himself will be able to delete incriminating data from the phone.

The United States and California argue that information on a cell phone may nevertheless be vulnerable to two types of evidence destruction unique to digital data — remote wiping and data encryption. Remote wiping occurs when a phone, connected to a wireless network, receives a signal that erases stored data. This can happen when a third party sends a remote signal or when a phone is preprogrammed to delete data upon entering or leaving certain geographic areas (so-called "geofencing"). See Dept. of Commerce, National Institute of Standards and Technology, R. Ayers, S. Brothers, & W. Jansen, Guidelines on Mobile Device Forensics (Draft) 29, 31 (SP 800-101 Rev. 1, Sept. 2013) (hereinafter Ayers). Encryption is a security feature that some modern cell phones use in addition to password protection. When such phones lock, data becomes protected by sophisticated encryption that