“Riverside Police Officer Ryan Railsback told Nexstar that his department is unaware of any such physical evidence”
Sour grapes.
Also, not a refutation. They’re saying “Squirrel!” on one hand and “sour grapes” on the other.
There was no DNA testing in 1966, so if they took any samples at all it would just be for blood type or hair analysis. They probably would not have been preserved anyway.
The only real DNA evidence in the Zodiac case comes from the stamps on the letters, and the only possibly reliable fingerprints are some that were recovered from Paul Stine’s cab. Besides that, there isn’t much physical evidence at all, unless they recover one of the firearms used or something like that.