Firstly, we will take the unusual step of acknowledging the Zodiac Killer at his word, when throughout his campaign of terror he constantly informed the authorities of his murder count, displayed on each subsequent letter or card. But how accurate were his claims, and could a timeline of potential Zodiac victims be attributed to the periods in between each correspondence, bearing in mind that his declaration of seven murders on the Dripping Pen card of November 8th 1969 could be attributed with almost complete accuracy, albeit the missing murder in August, has still yet to be resolved.
As stated previously, the months displayed at the foot of the Dripping Pen card could indicate the murder of David Faraday and Betty Lou Jensen in December, Darlene Ferrin in July, Cecelia Shepard in September, along with Paul Stine and Cheri Jo Bates in October. This meant six murders possibly attributed and one unaccounted for, due to his proclamation on November 8th 1969, indicating a total of seven victims up to this point.
So let us examine the period from this letter to the next confirmed Zodiac correspondence on December 20th 1969, that of the Melvin Belli letter, claiming he may lose control and claim a ninth and tenth victim. The suggestion of a search for a ninth and tenth victim, by inference, meant he had already claimed his eighth murder victim and it must have occurred between November 8th 1969 and December 20th 1969. So who was the most likely Zodiac victim, based on age, locality and nature of the crime during this time period.
One possibility is Betsy Aardsma, murdered in the campus library of Pennsylvania State University on November 28th 1969- although this crime has a number of question marks, including the locality- seemingly out of kilter with what we know of the killer to this point. There is, however, another interesting case that deserves closer scrutiny.
Leona LaRell Roberts (16), a resident of Napa, disappeared on December 10th 1969 from her boyfriend's apartment at 749 Tormey Avenue, Rodeo, feared kidnapped, after a neighbor recalled screams. Her nude body was eventually discovered on December 28th 1969 on a beach by Bolinas Lagoon, Marin County.
Contra Costa County detectives found a 1963 Napa class ring on her finger- inscribed on the inner surface of the ring were the initials J.A.S.
Although the cause of death was unclear, there was a suggestion of ligature marks on Leona Roberts wrists and ankles. According to Christopher J Farmer on his Opordanalytical article, a link to the Zodiac Killer was formulated with Gareth Penn being proposed as the prime suspect. Although this is an extremely well constructed article, with many interesting thoughts, it requires many leaps of faith to arrive at its conclusion- possibly too many to suggest this as a credible hypothesis.
In this article he suggested a link between the Dragon Card and 3141 Paradise Drive, Tiburon as a possible burial site of Zodiac victims. This area is located 23 miles east of Bolinas Lagoon.
Also on December 1st 1969 Elaine Davis (17) disappeared from from her home in Walnut Creek, Contra Costa County, California. She was abducted during the evening hours through a sliding rear window. Two and a half weeks later on December 19th 1969 her body was discovered floating off Light House Point, Santa Cruz, California, however, due to investigators misinterpreting the age of the victim at the time, her identity was only realized 31 years later when officials exhumed the body in 2000.
No link was ever ascertained between the murder of Elaine Davis and Leona Roberts, however, both victims fell within the correct age, area and timeline of the Zodiac Killer.
The Melvin Belli letter was mailed on the first anniversary of the Lake Herman Road double murder of David Faraday and Betty Lou Jensen on December 20th 1968. This correspondence was authenticated by the inclusion of a cut piece of Paul Stine's shirt, a taxicab driver callously gunned down in the Presidio on October 11th 1969.
But what is interesting about the letter, is that it mentions a possible ninth and tenth victim- and bearing in mind three of his previous four attacks were on lone couples, the suggestion of a likely future double attack, would place Solano County deputies on high alert, with deserted lovers lane areas a priority for extra patrols. The threat in the Vallejo area, however, never materialized.
On April 20th 1970, exactly four months later, the 'My Name is....Letter' landed on the doorstep of the San Francisco Chronicle. In this letter the Zodiac included a Bus Bomb Diagram, although more chillingly, was the declaration of 10 murders placed beside his now infamous crosshairs symbol. So who were his ninth and tenth victims.
Exactly bisecting the dates of the Melvin Belli letter and the 'My Name is...Letter' were the murders of John Franklin Hood (24) and Sandra Garcia (20), brutally stabbed on a Santa Barbara beach on Saturday 21st February 1970. Had the Zodiac lost control as he had asserted in the Melvin Belli letter, with this double murder moving his victims count ominously forward to number 10.
Moving forward two months to the Button letter on June 26th 1970, the Zodiac claimed 12 murders. He also stated he had "shot a man sitting in a parked car with a .38".
The only event that tallied with the Zodiac's claim was the murder of police officer Sgt Richard P. Radetich (25) on June 19th at 5.25 am, who was gunned down by three shots from a .38 caliber revolver at point blank range through the driver side window of his vehicle while in the process of serving a parking ticket. He was seated in his police car by 643 Waller Street, when it is believed another vehicle pulled alongside and an occupant opened fire. Officer Richard Radetich would die 15 hours later.
However, the Zodiac Killer, who almost always gained extreme pleasure from his mockery towards the police and authorities, only referred to his victim in the Button letter as a 'man', apparently failing to capitalize on the situation.
This appears to shed reasonable doubt that he was responsible for the murder of Sgt Richard Radetich, although the caliber of the weapon was correct.
The disappearance of Donna Ann Lass (25) from the Sahara Tahoe Hotel on September 6th 1970 seemed to push the Zodiac's murder count to 13, with the Halloween card mailed on October 27th 1970 proclaiming a possible fourteenth victim, arriving just two days after the murder of Nancy Bennallack (27), a court reporter, on October 25th 1970.
Finally, onto the Los Angeles letter, mailed on March 13th 1971, where he laid claim to an estimated 17 or more murders.
In this letter he stated "I do have to give them credit for stumbling across my riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there".
He was apparently referring to the fact that detectives had forged a link between the Zodiac Killer and the senseless slaying of Cheri Jo Bates in Riverside on October 30th 1966, claiming there were many more victims in that region.
One such attack, was the Robert Domingos (18) and Linda Edwards (17) double murder on June 4th 1963. The young couple were gunned down on a beach near Tajiguas Creek, Lompoc, Santa Barbara County.
The killer had initially attempted to bind the couple, reminiscent of the Lake Berryessa Attack on Bryan Hartnell and Cecelia Shepard on September 27th 1969. But clearly, if the Zodiac was responsible for this couple's murder, along with Cheri Jo Bates, then his murder total should have read 8, by the mailing of the Dripping Pen card on November 8th 1969, which clearly it didn't. The suggestion of "there are a hell of a lot more down there", seems to conflict with his declaration on the Dripping Pen card of seven murders.
The only reasonable explanation being, that these murders were not committed under the Zodiac umbrella. A pseudonym he would only adopt just prior to the 'Debut of Zodiac' letter, received by the San Francisco Examiner on August 4th 1969. The killer may have belatedly attached the 1963 murders of Domingos and Edwards, and the Riverside murder of Cheri Jo Bate to the Los Angeles letter claiming 17+ murders. This may explain the increase from the 14 victims claimed in the Halloween card approximately five months earlier.