Despite decades of investigation and many named suspects, no offender has ever been definitively confirmed by physical evidence or a court; police named only one official suspect, who died in 1992 without being charged.
What would resolve this A confirmed DNA match between crime-scene evidence and a specific individual, of the kind that resolved the Golden State Killer case through forensic genetic genealogy, or a conclusive decoding of the still-unsolved Z13 and Z32 ciphers naming the sender.
Wikipedia: Zodiac Killer