In the case of the Zodiac Killer, any DNA he deposited on the letters, Lake Berryessa bindings or Paul Stine's taxicab, would today have provided enough DNA for analysis in CODIS (Combined DNA Index System), where the crime scene forensics of a particular crime could be entered, in search of a match to a an offender already held on the database. This technique however, is totally dependent on the murderer, in our case, having a previous conviction, otherwise a direct match could never be made. The use of a familial DNA profile has led to the closure of many cold cases, where a close relative has been found on the database and been linked to the current DNA being analyzed through family lines, resulting indirectly to the capture or identification of a criminal, sometimes decades after their crime was committed.
Recent developments have revealed a tantalizing glimpse into the future, offering the possibility to deliver the Zodiac Killer's identity right into the palms of our hands. This has been covered previously, but it will be expanded here in a little more detail.
This new technique removes the need for the Zodiac Killer's or indeed any blood relative to have committed any previous or subsequent crimes and render the necessity of comparison tools such as CODIS redundant, in this instance. It all comes down to the Y chromosome, passed from one generation to another, along the male lineage, in exactly the same manner as ones surname is also passed along. Thereby providing an indelible connection between the Y marker and a man's surname, as an alternative crime fighting tool, and one that could provide us with the exact surname of the Zodiac Killer. This may not deliver the murderer of five people in Northern California on a platter, however, it would at the very least remove all but one of the high profile suspects or most likely all of them from our Zodiac researchers lists. But how does it work in practice and what are its limitations.
When a surname is carried down family lines for generations, an undeniable link exists between the surname and the Y chromosome, so when samples of DNA are retrieved from a current crime scene or from cold cases, they would have the Y chromosome isolated and bearing in mind its close connection to family lineage, used to reveal a surname. This of course would require a database, similar to CODIS, but this time when the Y marker is entered, the possible surname is availed to the observer. The police investigators would then use this to narrow down the field of view, regarding potential suspects and by the same note, remove suspicion from some entirely, reducing man hours and wasted blind avenues.
Research has shown the rarer the surname, the greater the chance a common ancestor is shared and this analysis can be viewed in greater detail in the two articles listed at the foot of this page. There are nevertheless drawbacks to any technique, in this case adoption and illegitimacy are two such examples, so caution needs to be applied.
The bottom line, is that the confirmed Y marker of the Zodiac Killer may just provide us with the name, that his ciphers promised, but always failed to deliver.