I have been curious about when/where destruction of evidence takes place. Presumably during the crime, the perpetrator does their best to hide the evidence. Do

I have been curious about when/where destruction of evidence takes place. Presumably during the crime, the perpetrator does their best to hide the evidence. Does it only become destruction after you have been informed the police are interested in you? What if you do it before a warrant is issued? What if your device will self destruct if a password is not entered every N days and you withhold that information?