A grand jury indicted Hupp in December 2016 for allegedly killing Louis Gumpenberger.
Prosecutors claim Hupp murdered Gumpenberger after claiming he attacked her at her home. An O'Fallon police investigation revealed evidence that Hupp plotted the whole thing and picked Gumpenberger as her pawn.
Hupp's trial is scheduled for October 3.
In February, Hupp's lawyer asked the court to bring in jurors from another county. Prosecutors insist there's a large enough jury pool in St. Charles County to find unbiased jurors.
According to St. Charles County Prosecuting Attorney Tim Lohmar, Hupp would be the first woman Missouri has put to death since Bonnie Heady in 1953.