We know that the taxicab keys were taken from the scene by the Zodiac Killer. We also know he took the swatch of Paul Stine's shirt, which he used in his mailings to verify he was the letter writer. The Zodiac, to our knowledge, never sent any packages and tends to negate the idea he may have taken the keys to possibly mail at a later date, firstly because he didn't and secondly he opted for the far more time consuming method of carefully tearing a strip of Paul Stine's shirt, when clearly the taking of a set of keys was the far quicker option. Is it therefore not reasonable to assume he took the keys for a completely different and logical reason, in that he had at some point in the taxicab journey touched them. If he was wiping down the taxicab and had inadvertently left blooded fingerprints, it is fair to say he was likely not wearing gloves. Had he touched the keys, handling them to wipe them down is counter productive and trying to wipe them down while they are 'free swinging' in the ignition is difficult and by the same token it is far quicker to just remove them altogether.
Therefore their removal appears the logical choice from his standpoint and appears to lend weight he had commission of the vehicle at some point during that night. Does this indicate the possibility of a Washington and Maple murder and why the taxicab was found one block later. During the shooting of Paul Stine his taxicab may have stalled, after all he was on a run through to 500 and 9th, his engine was still running and the vehicle would not have been placed in park, necessitating Zodiac's intervention to gain control of the taxicab and coast it away from the immediate vicinity of the gunshot, that nobody heard at Washington and Cherry. There appears little other reason to remove keys he never used in any of his subsequent communications, along with the wallet, as both are bulky items and both are incapable of being mailed in standard letter form and something he always did.

