Unless it's found in the middle of nowhere, and maybe not even then, how does one determine if a piece of trash is there by the deliberate act of littering? As

Unless it's found in the middle of nowhere, and maybe not even then, how does one determine if a piece of trash is there by the deliberate act of littering? As well, lots of trash has several people's DNA with no one individual having the majority such as product packaging, and that's the most likely to be littered.