Antonio "Tony" Marconi (1961–2018), appearing as a recurring character in Season 1 and Season 5 of Criminal Case, was a suspect in the murder investigations of three people before turning out to be the killer of Vipers' leader Salvador Cordero in Into the Vipers' Nest (Case #11 of Grimsborough). As a jailed convict, he reappeared as a suspect in the murder investigations of two more people in Grimsborough.

After being released from prison during the events of The Conspiracy, Tony reappeared as a suspect in the murder investigations of three people and a quasi-suspect in five other cases before being murdered in Up in Flames (Case #36 of The Conspiracy). In his childhood, he made a minor appearance in What Happens in Vegas... (Case #9 of Travel in Time).