Person of interest: a person who is believed to be possibly involved in a crime but has not been charged or arrested – www.merriam-webster.com
The above term has been used in law enforcement since 1937, according to Merriam-Webster. I don’t know what—or who—happened in 1937, but more recent examples of “person of interest” are Richard Jewell (innocent), Scott Peterson (not innocent), Andrew Cunanan (also not innocent), and James Caviezel (fictional).