On December 29, 1969, the San Francisco Police Department sent a list of twenty suspects to the Bureau (here the telegram) via the local FBI office for a review of the Zodiac case.
In their reply dated January 12, 1970 (here), FBI experts point to an oddity in the December-29-list. That is, the fact that the suspects have “same or similar birth dates”.
Caught at a loss, agents in San Francisco respond on January 14 (here), claiming they have just been informed that a self-proclaimed Zodiac phoned the home of the stars’ lawyer Melvin Belli saying it was his birthday.
On December 20, 1969, the real Zodiac sends a letter to attorney Belli’s residence in San Francisco. The killer writes: “I cannot remain in control for much longer.” The day coincides with the one Zodiac killed a teenage couple on Lake Herman Road in 1968.
In the same period the real Zodiac sends the letter to Belli, a man who claims to be the serial killer makes a phone call to the attorney’s house. Belli’s housekeeper, Erna, informs the caller that the lawyer is in Europe. Her interlocutor replies:
“I can’t wait, today’s my birthday”.
Both Zodiac and the anonymous man tried to contact Belli at the same address, in the same period, expressing with similar expressions the impossibility of “waiting” or “holding back”, and the same urgent need to talk to him.
When exactly did the phone call date? It is unknown, because the personal information on the December-29-list was redacted from the FBI Zodiac file release. However, it can be restricted to a period of 9 days: December 20-29, 1969.
According to an article in the San Francisco Chronicle on December 29, 1969, in fact, Belli was “en route” to Germany on December 20. So he was definitely already in Europe or was about to arrive.
Taking into account that Belli’s letter is only opened after Christmas and the release of the news dates back to December 27, it is likely that whoever called Belli home did so before the public was informed of the letter. All the more reason to believe it was the real Zodiac.
There is a reason if the serial killer decides to contact Belli. In October 1969, an impostor – who would later be tracked down (see this FBI communication) – phoned a San Francisco TV show claiming to be Zodiac and managed to talk live with Belli. The police excluded that he could hear it being the real Zodiac as none of the witnesses who spoke it recognized the voice.
The same Zodiac in the cipher Z340 on November 9, 1969 claims that it was not he who spoke on television. Perhaps, the serial killer decides to take the place of the impostor and contact Belli to take back what in his view is rightfully his.
Even if this source does not place the birthday of the false Zodiac in the period 20-29 December, it is still possible that he could be the caller.
One thing is certain. It would be possible to trace the day the “birthday call” took place, having available the December-29-list without redactions.