The Supreme Court rejected those arguments and upheld an Appellate Court ruling.
Senior Assistant State's Attorney Robert Scheinblum said Monday's decision was important for public safety.
"The Supreme Court's decision ... recognizes the Superior Court's ability to protect public safety by conditioning an incompetent murder defendant's release on the requirement that he submit to periodic competency exams while he remains at liberty," Scheinblum said.
It wasn't clear Monday where Custodio is living now.
In court documents, Pieszak said Custodio suffers from a brain disorder and has received Social Security disability benefits for the past four decades. Pieszak said Custodio believes John F. Kennedy is still the president and thinks he is 54 years old.