In the police report regarding the attack at Lake Berryessa, Bryan Hartnell is quoted as estimating the Zodiac Killer's age as 20 to 30 based on voice concept. Despite the analysis of age based on somebody's voice being wholly unreliable, the age range given by Bryan Hartnell is often used by Zodiac researchers to partly validate a proposed person of interest who is within this range. The same is done with David Slaight, who received the phone call from the Zodiac Killer seventy minutes after the Lake Berryessa attack, who appeared to corroborate the earwitness testimony of Bryan Hartnell by describing the voice he heard at 7:40pm on September 27th 1969 as young (possibly early twenties).
Bryan Hartnell and David Slaight However, the following observations show just how unreliable it is to estimate somebody's age based on nothing more than hearing their voice. Bryan Hartnell and David Slaight's thoughts that the Zodiac Killer may have been somebody in his twenties will be called into question by none other than Bryan Hartnell and David Slaight. The San Francisco Chronicle released a newspaper article on October 24th 1969 entitled "That Wasn't Zodiac, Say 3 Who Know", in which Bryan Hartnell, David Slaight and Nancy Slover listened to the recorded voice of "Sam" on the Jim Dunbar TV Show. The article stated that "Bryan Hartnell told Napa County homicide detectives he remembers Zodiac's voice as being much older and deeper than the one heard in the series of telephone calls to KGO-TV. His opinion was backed up by Napa police Patrolman David Slaight and Vallejo police clerk Nancy Slover, who have also heard the real killer's voice".
San Francisco Chronicle October 24th 1969 The voice of "Sam" was later found to be that of Eric Weill, who pretended to be the Zodiac Killer when interviewed by Jim Dunbar and Melvin Belli on October 22nd 1969. Therefore, Bryan Hartnell and David Slaight both described the Zodiac Killer's voice as "much older" than Eric Weill, who was aged 29 in 1969. This seemingly contradicts Bryan Harnell's earlier police report of a 20 to 30 years estimation, and David Slaight's recollection of a man possibly in his "early twenties". Somebody described as "much older" than 29, must be at least 35 to 40 years of age. Of course, both Bryan Hartnell and David Slaight could have been influenced by their perception of the voice of "Sam" (Eric Weill) believing him to be much younger when they heard the recordings. They may have thought "Sam" to be about 18, thereby making their "much older" perception of Zodiac still viable as somebody in their mid-twenties, or up to 30 years. This appears like a reasonable explanation for the discrepancy. However, if "Sam" was 29 years of age and sounded 18 years of age (11 years younger), then the Zodiac Killer could have been 39 years of age at Lake Berryessa, yet sounded like a man aged 28, in line with Bryan Hartnell's 20 to 30 age estimation. If Bryan Hartnell can mistake the age of "Sam" by at least a decade, he can mistake the age of Zodiac by the same amount at Lake Berryessa.
This is why perceiving individuals age based on the sound of their voice is inherently flawed. So when Zodiac researchers use the interpretations of earwitnesses and eyewitnesses to argue their case for a suspect (or person of interest) fitting the desired age range, they employ confirmation bias and augment the attributes of some and not others. The testimony of Bryan Hartnell, Donald Fouke, Michael Mageau and the three teenagers, regarding the age of the Zodiac Killer, will be dissected meticulously to discredit and promote each that best fashions a case for their person of interest. Interpreting information to conform to an existing belief system, while ignoring information that doesn't conform to an existing belief system, is highly beneficial in crafting a false narrative and magnifying the likelihood an individual will be perceived as the Zodiac Killer by the reader. The problem is that everybody does it, but it's only recognizable in others.
This is why perceiving individuals age based on the sound of their voice is inherently flawed. So when Zodiac researchers use the interpretations of earwitnesses and eyewitnesses to argue their case for a suspect (or person of interest) fitting the desired age range, they employ confirmation bias and augment the attributes of some and not others. The testimony of Bryan Hartnell, Donald Fouke, Michael Mageau and the three teenagers, regarding the age of the Zodiac Killer, will be dissected meticulously to discredit and promote each that best fashions a case for their person of interest. Interpreting information to conform to an existing belief system, while ignoring information that doesn't conform to an existing belief system, is highly beneficial in crafting a false narrative and magnifying the likelihood an individual will be perceived as the Zodiac Killer by the reader. The problem is that everybody does it, but it's only recognizable in others.
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