Not to split hairs, but- if the ISB investigators immediately AFTER the incident did not request the computers, then they remained the property of the dive shop, which owned them, no? You call it "Linnea's" computer- but it wasn't, was it? Wasn't it a rental from the dive shop- it was the Dive Shop's computer that Mills rented, right?
Therefore, if the owner (the dive shop) voluntarily surrendered the computers THEY OWNED to the PADI investigators, who then began analysis - what issue is there?
Until you sued civilly and Discovery was ordered, AND you demanded them, or a criminal investigation subpoenaed them, what exactly is the legal issue in what happened from a "chain of custody" perspective? As far as I can tell, there is none.
They (PADI) safeguarded potential evidence, via counsel, did not destroy it, and engaged in their own investigation with voluntarily acquired dive computers directly from the owner (the diveshop) of those computers, after criminal investigators passed on taking them.
Or are the facts something else?