Fourth Amendment
Surreptitious video recording made by invited guest in private apartment does not violate 4A, as the only things recorded were within the eyesight of an invited informant who would have been able to testify to them.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2016/D02-01/C:15-2008:J:Kanne:aut:T:fnOp:N:1696062:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.