Can the defenders do the same as prosecutors and use lack of WebMD "how long does it take to die in car" search as evidence as well ? Are they going to get access to internet search history of the accused ? They supposedly obtained the information from seizing and browsing of the computer. In that case it won't be very convincing if accused use the same method: "here, go seize my computer and see there is nothing there!". That creates asymmetry: one kind of evidence could potentially be used to make given hypothesis more believable but lack of the evidence couldn't be used against it. It seems to me, it's very dangerous state of affair. Especially if it's police/prosecutors who get easier access to this kind of evidence (the defenders would have to for example ask NSA for search history to make it believabl while prosecutors only need to seize the computer and if they do seize it an find nothing their case won't be any weaker as they just won't present the fact).