Police say the couple decided to murder the married man only because “They wanted to kill someone together.”
They did so, according to court documents, on the day of their three-week wedding anniversary.
Quinn and Bremigen are the lead investigators in the case that has attracted worldwide attention.
Police earlier this week were seen leaving 101 N. Water St. with an evidence bag, and would not comment whether they found the knife that killed LaFerrara.
Miranda Barbour told police she used a knife to stab LaFerrara and that days later, she tossed it in the Susquehanna River in Selinsgrove.
LaFerrara was stabbed 20 times, Northumberland County Coroner James Kelley said.
Miranda Barbour told police she knew the exact spot where she threw the knife, court documents said.
Elytte Barbour and Miranda Barbour are due to appear before Sunbury District Judge Ben Apfelbaum on Dec. 20 in separate hearings.