Perhaps R99 was the Zodiac Killer?
That would count as a "qualification", wouldn't it?
Good try! At least you are thinking for a change. Now why don't you start at square one and see if you can determine what actually constitutes the ciphers.
Full disclosure, I am not the Zodiac and I was not in California on the dates of any of his murders to the best of my knowledge.
But I had been in California the week previous to the Riverside murder which some media types claimed the Zodiac was responsible for. However, I was on the east coast on the evening of that murder.
Full disclosure again, it is highly unlikely that the Zodiac had anything to do with the Riverside murder. The Riverside Police had a viable suspect for that murder, but the media and the Zodiac was claiming that he did it so their suspect got off the hook.