In the event of an illegal act itself? One could argue it for days, but no matter—the perv has been outed and will rightly be shunned.
“In the event of an illegal act itself?”
It depends on who did the illegal act. For the Exclusionary Rule and so on to apply, “illegally seized” means specifically that a government actor or proxy violated the law to obtain the evidence, not that the evidence was obtained in the course of a crime by a private citizen.
All of this is rooted in court decisions on the workings of the Fourth Amendment, which puts a curb on -government- actions. It was not even applied to the states until 1961, but only to the US government. It does not apply to private persons.