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 could be entered into the database to search for a match to an offender already contained within it. However, this technique is totally dependent on the murderer 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 effectively 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. This would providie a correlation between the Y marker and a man's surname, and thereby provide an alternative crime fighting tool - 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, and most likely all of them from our Zodiac researchers lists. But how does it work in practice and what are its limitations?
Research has shown the rarer the surname, the greater the chance a common ancestor is shared. 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.