Demanding a speedy trial is the one defense strategy that has a chance to defeat a prosecution notwithstanding strong evidence.
You demand a speedy trial, knowing the case is still being investigated and put together. The deadlines for disclosure come up fast, and the prosecution misses them because it is under-resourced and maybe not competent to try a capital case due to lack of experience. You might find judges who have never tried a mass murder or any other case that received national press attention, and you hope for mistakes there, especially about venue change issues, due process issues, free press/fair trial issues, and so forth.
The strategy worked well recently in a Colorado case,
People v Morphew.
I hope the local prosecutor can call on expert help organizing the evidence, meeting disclosure deadlines, and trying the case, just as investigators called on help from the FBI.