Yes, Erik Menendez was the co-author of a screenplay about a young man who kills his parents and inherits $157,000,000. The script that was completed — and shopped around Hollywood — before the murders.
No, it was never included as evidence in either of the two trials.
From a craft standpoint, one of the things I have to applaud Robert for is brilliantly weaving the multiple and complex storylines together to show the many aspects of this strange story, including the brothers’ own account of the days leading to the murders as well as when witness statements conflicted on certain points.
He was still writing the final chapter as the book went into production because new facts kept coming up.
Normally that would be an editor’s nightmare, but in this case it was a welcome challenge to have an author able to capture the latest scoops.