On December 29, 1969, the office of the FBI in San Francisco sent a list of suspects’ names (this one) provided by the police to the Identification Division for a checking related to Zodiac.
In their response dated 12 January 1970 (here), the experts of the Identification Division pointed out the suspects in the list had «same or similar birth dates» .
Probably after the response of the FBI laboratory, noting the experts’ observation, the agents in San Francisco asked the SFPD an explanation to the suspects’ birth dates. On January 14, they reported (here) to the Director and Identification Division that the SFPD told them a self proclaimed Zodiac had called attorney’s Melvin Belli’s home saying it was his birthday. They did not specify when the phone call had been made.
“TODAY’S MY BIRTHDAY”
“I can’t wait. Today’s my birthday”, the self-proclaimed Zodiac said to attorney’s housekeeper, Erna, who told the caller that Belli was in Europe.
In the same time period, on 20th December 1969, the real serial killer mailed a letter to Belli to the same address asking for haste towards him using an analogous expression: “I cannot remain in control for much longer”. Exactly one year before, he had killed a couple of teenagers on Lake Herman Road.
Joe Bevilacqua’s birthday is on 20th December, which also is the last day of staying in the newsstands of the issue of the magazine used by the Monster of Florence to compose his letter to Della Monica, in 1985.
AT THE END OF DECEMBER
According to the San Francisco Chronicle, Belli was in Europe when Zodiac’s letter postmarked December 20 was mailed. The envelope was not opened before Christmas and the news was not disclosed before December 27 (S.F. Sunday Examiner & Chronicle, December 28, 1969), which almost completely excludes that the call had been made by someone who, other than Zodiac, was aware of his message to Belli.
This supports the hypothesis that the call was made by the real serial killer.
The date of birth of the mythomaniac who had called Belli on television in October 1969 and was traced after another phone call to the KGO-TV (FBI communication) did not fall within December, according to this source.
Even if the public does not know for sure if it was the real Zodiac the man who called Belli and on what day the phone call occurred, if it was the serial killer, December 20 seems to be the most probable date of the “birthday call”. Obviously, in order to verify this deduction, the police could check the date of births in the 29 December list.