Are their any reasons to believe this crime could have fell into Zodiac territory? Possibly a few, but they by no means sway the balance towards a substantial argument in favor. Nevertheless, we shall examine the slim pickings and show what has been observed over the years to contemplate such a link.
It was believed the Zodiac Killer may have been driven by dates - although this is speculative. The attack at Blue Rock Springs Park was one year prior to the murders of Thomas Victor Dolan (17) and Homer Clyde Shadwick (19) in Santa Barbara. The Melvin Belli letter was received exactly one year after the Lake Herman Road double murder. The murder of Betsy Aardsma was nearly three years to the day after the 'Confession' letter, mailed by the alleged murderer of Cheri Jo Bates on November 29th 1966, if indeed this was genuine Zodiac correspondence. And Joan Webster disappeared on November 28th 1981, exactly twelve years after the Pennsylvania library stabbing. These dates taken in isolation mean very little from the standpoint of evidence, so let us take a look at the Riverside Desktop Poem, discovered sometime in the December of 1966, just teo months after the Bates murder. It read "blood spurting, dripping, spilling all over her new dress. Oh well it was red anyway."
A highly controversial letter mailed in 1978, alleging it was from the Zodiac Killer, began with the words "This is the Zodiac speaking I am back with you". On November 28th 1994, exactly 25 years after the Betsy Aardsma murder, an employee of the library found a candle had been lit and placed in the location of the murder. A message written on the floor using a marker pen read "RIP Betsy Aardsma, born July 11th 1947, died November 28th 1969. I'm back." Additionally, a postcard had been mailed to police sometime in the 1970s with the wording "You never did catch the guy who killed that c**t in the library". But these were considered malicious hoaxes - and not considered to have been authored by the killer.
The Betsy Aardsma murder occurred exactly 48 days after the last confirmed murder by the Zodiac Killer - that of Paul Stine on October 11th 1969 in Presidio Heights. The next letter mailed on December 16th 1969 claiming to be Zodiac, was the disputed Fairfield letter, mailed inside of one month after the young woman's death, depicting a knife dripping with blood and the wording "The Bleeding Knife of Zodiac".
The 340 Cipher and 'Dripping Pen' card on November 8th 1969, followed by the 'Bus Bomb' letter one day later, opened up with the line "This is the Zodiac speaking up to the end of Oct I have killed 7 people". The Melvin Belli letter, known to be authentic, was mailed on December 20th 1969 with the lines "I am afraid I will loose control again and take my nineth and posibly tenth victom". So, by inference, he had already claimed victim number eight sometime between November 9th and December 20th, with the Betsy Aardsma murder pretty much bisecting these two dates. However, the Zodiac would make no direct mention of this crime in any of his remaining correspondence over the next five years.
The murder was committed on a Friday, one day after Thanksgiving. Could the Zodiac have been visiting relations during the holidays, providing him with the opportunity to take his murderous campaign further afield and "change the way the collecting of slaves. I shall no longer announce to anyone. When I committ my murders, they shall look like routine robberies, killings of anger, + a few fake accidents, etc". Admittedly, the Betsy Aardsma case is one of the weaker Zodiac associations, as there is clearly little or no evidence linking Northern California's most elusive killer to the Penn State University on that fateful day - although it is most certainly not beyond possibility.
Please watch this informative Youtube video by David DeKok, a reporter for the Patriot News in Harrisburg, Pennsylvania.