The question here is whether the police were in investigation mode. I believe it is an overreach to claim that everybody at a border was going through an investigation. And it is also a overreach that everyone who is selected for search at the border is under investigation.
An investigation doesn't need to have begun. All that's required is that you intended to destroy evidence in the event of an investigation.
https://www.law.cornell.edu/uscode/text/18/1519
> Whoever knowingly alters, destroys, mutilates, conceals, covers up, falsifies, or makes a false entry in any record, document, or tangible object with the intent to impede, obstruct, or influence the investigation or proper administration of any matter within the jurisdiction of any department or agency of the United States or any case filed under title 11, or in relation to or contemplation of any such matter or case, shall be fined under this title, imprisoned not more than 20 years, or both.
"... or in contemplation of..."
https://www.subjecttoinquiry.com/2014/04/obstruction-of-cont...
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The defendant need not know a matter was pending or within federal jurisdiction. Instead, the “knowingly” element refers only to the obstructive conduct. United States v. Moyer, 674 F.3d 192, 208 (3rd Cir. 2012). The federal nature of the statute’s prohibition is a jurisdictional requirement, but not a substantive element under Section 1519. United States v. McRae, 702 F.3d 806, 834 (5th Cir. 2012).
No nexus requirement. Given that an investigation or matter within federal jurisdiction need not be initiated or even pending at the time of the obstructive conduct, the government need not prove any connection between the alleged obstructive conduct and the federal matter. Moyer, at 209; United States v. Gray, 692 F.3d 514, 519-20 (6th Cir. 2012).
Materiality is not an element. As an example, falsification through omission from a log or report can support a conviction, without proof of the materiality of the omission. Powell, at 356; Moyer, at 207-08.