Quick answer: Ian Brennan has discussed possible future Monster subjects, but these are not official Season 5 announcements.
Possible subjects discussed
Recent reporting says Brennan has discussed BTK, Ted Bundy, the Green River Killer and Luigi Mangione as possibilities. They should be treated as ideas, not confirmed subjects.
How the process works
Brennan says the creators keep multiple possibilities in development and sometimes abandon them.
Another idea from Charlie Hunnam
Hunnam separately pitched a possible story about Roy DeMeo. Entertainment Weekly reported that Ryan Murphy was not interested in that organized-crime direction at that time.
Current status
No specific Season 5 subject is confirmed in current official Netflix material.
Sources: The Hollywood Reporter; Entertainment Weekly
Fact-check note
This article distinguishes the Netflix dramatization from documented history. Lizzie Borden was acquitted in 1893; claims about guilt, private relationships, motives and events not established by surviving records are described as fictionalized or disputed rather than settled fact.
Netflix Tudum: The True Story · Netflix Tudum: Ending Explained · PEOPLE: Fact vs Fiction · PEOPLE: Emma/Lizzie Fact Check
Related: Monster: The Lizzie Borden Story Finale Explained — What Ian Brennan Says About the Ending
Related: Will There Be Monster Season 5? What Ian Brennan Has Said So Far
