Mark Riebe
Mark Riebe is an American man convicted of the murder of a young woman in Florida in 1998, a case that remained unsolved for years before being reopened with new evidence. He was later linked to the killing through advances in forensic investigation. Riebe was convicted and sentenced to life imprisonment. His case highlights how cold cases can eventually be solved through persistence and improvements in investigative techniques.
Mark Rust
Mark Rust is currently incarcerated for two counts of murder, notably for the murder of Maya Jakic in 1999.
Mark Twitchell
Mark Twitchell is the individual identified as a killer, known for being accused and convicted of abducting and murdering Alberta farmer Johnny Altinger in 2008.
Marshall Applewhite
Marshall Applewhite was the leader of the Heaven's Gate cult, which culminated in the mass suicide of its members in 1997

Marshella Chidester
Marshella Chidester is an American woman convicted in connection with a fatal vehicle incident in Michigan in 2024. The event occurred when she drove into a building during a private gathering, resulting in multiple deaths and injuries. The case gained national attention due to the circumstances of the incident and the loss of young lives. Chidester was later convicted and sentenced to a lengthy prison term.
Mary Ann Cotton
Mary Ann Cotton is a notorious Victorian Era serial killer, known as 'The Black Widow', who poisoned multiple family members.
Mary Bell
British child who was convicted for the murder of two young boys in Newcastle upon Tyne, England, in 1968