This is a good question, but I don't think it's one I'm able to offer you a firm answer on. The way I most often hear this discussed is as a "CSI Effect," where juries conditioned by hours of courtroom dramas expect fancy scientific evidence, crystal-clear 911 telephone call audio, and an abundance of physical evidence. Actual criminal practice doesn't work that way, of course.

Anecdotally -- one of my colleagues is a 15+ year federal trial vet and this is what she tells me -- the CSI Effect is real, and you'll see prosecutors preempt defense complaints ("the prosecution won't put on a single speck of DNA evidence," etc.) by mentioning in their opening and closing why this type of case wouldn't involve that type of evidence, due to (for example) lack of resources or adequate alternative evidence.

But these are anecdotes, not data!! And therein lies why I can't give you a good answer...:

It appears there are a number of papers on this very subject, which means it descends into a question of social science rather than history. You might want to give r/AskSocialScience a shot.

Though I can't give you an answer I hope that by giving you the right "search term" ("CSI Effect") I'm at least pointing you in the right direction :).