Why Do You Have to Be Ready to Go to Trial When You Indict a Case?

The prosecution had no idea that she had made this search the day that, you know, Kaylee went missing. This makes so much sense now why the prosecution had brought on Vass to talk about the jar of air analysis and chloroform. The fact that this information wasn't known to the prosecution is literally a too bad for the prosecution. You can't go back in time and re indict Casey or try to open back up the jury somehow for deliberation.