Originally Posted by
The Weasel
"Probable cause" is a very critical term in search and seizure law. I won't use one of the case decisions here, but try to provide one that I think is more appropriate for laypeople to live with. But first, one needs to understand something said repeatedly on the previous thread: There is no right to search a person (with or without a backpack) or their effects they are carrying (such as a purse, briefcase, shopping bag or backpack) unless (1) a warrant has been issued by a neutral magistrate or judge (either way, a part of the judicial branch) authorized to issue warrants after factual information presented to her that "probable cause" exists for the search and a finding by her that it does, in fact, exists, OR (2) an exception exists such as (a) "protective search" or patdown for protection of officers, (b) "plain view" items that are immediately observable (example: pot in a baggie clipped to pack), (c) "consent" searches or one of several others. (If you're really interested in 4th Amendment issues like that, tell me, but there are better resources online than I'll be.) If a search doesn't fit one of those exceptions, there is no right to search.
NO one has the authority to perform an illegal search. Warrant-based searches must be performed by a person authorized in the warrant (usually by category, i.e. "Damascus Police Department" or some such thing). Protective searches or stops may be performed by law enforcement officers acting within their jurisdiction.
"The rules" are the same on the trail, at airports, and anyplace else in the US with the EXCEPTION of border zones, where Customs/Border Patrol agents have the right to search w/o warrants due to the nature of the border. That includes Entry Points and Border Crossings, as to both non-citizens and citizens alike.
"Citizen arrests" are possible but so risky that I would rather not comment, and I'll dodge that by saying it's off-topic. Otherwise, only law enforcement agents acting within their jurisdiction. There is a significant post on that in the early part of the original thread. Due to frequent "cross-deputizations", many state and federal LEO's are deputized to act outside their specific city/county/state, and if someone performs an arrest, displaying law enforcement credentials, you should assume they have the authority to do so, and leave that issue for post-arrest consideration by your attorney or, if you don't have one, yourself.
In this scenario, briefly, you have no "authority" to demand names, and absolutely no right to go into other people's packs. LEOs would want as much identifying information as possible, including names, if possible, and descriptions. She would not, though, be able to "go into their packs" to get your things, absent a warrant. Unless you saw the theft or saw your gear, and were willing to sign an affidavit, it is doubtful a warrant would issue. The police may question people, however, if they can find them, and people accused of crimes do a lot of stupid things, like consent to searches. That is the best, frankly, you could hope for. As for markings, the more permanent and/or indelible, the better. Serial numbers help, too.
(1) That's theft, not "finding. Depending on the value, it's either "simple" or "grand" theft, which are separate crimes with different penalties. (2) If not voluntarily returned, hitting someone would be an assault, and not justified. You can report the theft to the police. (3) Charges would be for theft. (4) No, without a complaining witness, police/prosecutors generally will not take a case further than a complaint.