Riverside PD & Ex-SF Cop on Zodiac Case Don't Believe Poste's The Killer

The Zodiac Killer has NOT been ID'd as The Case Breakers would have you believe -- at least according to cops who looked for the guy back in the day, but Case Breakers says the cops have refused to even investigate a possible connection.

Riverside PD tells TMZ ... the investigative body that came out Wednesday with its big get is probably wrong in its assumption Gary Francis Poste is the elusive serial killer.

RPD's PIO, Ryan Railsback, says the Case Breakers cite the 1966 murder of Cheri Jo Bates and evidence the group says it gleaned from studying the file as the basis of their conclusion.

Railsback says their initial suspicion the Zodiac was responsible -- based on letters they received at the time -- was nothing but a red herring. Railsback says if there was any evidence suggesting Poste was their man ... the force would've happily come forward with such info. But they haven't, 'cause he isn't.

That leads us to Frank Falzon, a former SFPD homicide inspector, who was once partners with the famed Dave Toschi -- in charge of the Zodiac case in the early days -- and who took over the file once Toschi left the picture. He, too, tells us ... he believes Poste ain't the guy.

His rationale -- Poste's name, from what he can recall, never came up as a strong possible suspect among the hundreds of names they had on file. It doesn't ring a bell to him.

But, here's the thing ... Case Breakers tells TMZ they contacted the Riverside PD and asked them to do a DNA test on the victim's hair and compare it with the DNA of Gary Francis Poste, and the PD refused. Case Breakers tells TMZ, the PD told them they believed the murderer was local to Riverside County and would not consider anyone outside the county. Case Breakers says the PD told them they were "100% sure" the murderer was not the Zodiac Killer and the police repeatedly refused to investigate a possible connection.

A source at Riverside PD tells us they do not have knowledge of CB reaching out regarding the evidence.

Falzon points to what he considers lots of circumstantial evidence the Case Breakers used in pinpointing Poste as the Zodiac -- which, in FF's view, isn't enough to draw that big of a deduction. In his eyes ... ID'ing the Zodiac would always come down to fingerprints and handwriting -- and based on what he saw in the CB's analysis, those factors were absent.