Zodiac's Age, like a lot of other things about Him, is open to speculation and/or interpretation dependant upon who it is Your asking. Some will insist that this killer, like the FBI statistics seem to imply, will be a White Male, Mid Twenties to Early Thirties. He will, most say, fall within the 'Expected' age range that the FBI Profilers suggest Serial Killers will be when they begin their reign of terror. However, lets not turn to statistic, let's not rely on odds of probability, let's use the facts as we know them to be to determine what the likely age of this offender was in 1969.
First, let's look at Bryan Hartnell and His comments. It is commonly mis-quoted that He suggested His hooded attacker had a young and youthful sounding voice. This, like many other things in the Zodiac case, is untrue. First, Bryan was asked to go along to listen to the voice that called in to the Jim Dunbar show claiming to be the Zodiac Killer. Here is what Bryan said after being played the recording...
"That's not Him. The voice on that tape isn't even in the range of what I remember the Zodiac's voice as sounding like. The voice of the man who stabbed me was much deeper and older sounding than that man on that recording." The article continues and states that Bryan's opinion was: "Backed up by Napa's David Slaight and Vallejo's Nancy Slover who both had also heard the voice of the real killer."
So, that is age recognition via audible educated guessing, lets now turn to actual eye witnesses recollection of Z for age approximation. This eye witness is a witness with extra credibility! He isn't just your average man on the street eye witness, this is a trained observer and SFPD Patrol Officer, Donald Fouke. Lets examine both a statement He made mid Nineteen Eighties and then again in 2007. First, the earlier of the two:
"The individual I saw that Night was a White Male Adult, Thirty Five to Forty Five Years of age, Five ft Ten and weighing approx. 180 to 210lbs." Straight forward enough, in a nut shell, a middle aged white guy. Let's go to 2007:
"I noticed, on the North side of the street, A White Male Adult wearing a derby, or three quarter waist length jacket that had elastic at the waist and on the cuffs and regular flap down collar. He had a crew cut, He was wearing rust coloured pleated trousers which were unusual for that time. He had on engineering type boot, a lot cut show, tan in colour." Fouke gave no Approx. Age audibly here but a composite was shown while He described the male. This was the face of the WMA as remembered by Don Fouke, the trained observer: