This new system works by taking the Y chromosome from a suspect's DNA and instead of searching for a direct match, which of course is wholly reliant on the suspect being in the database, this system removes that need. In other words, the suspect does not have to have committed a prior offence to be matched. It works by creating a database of thousands of different surnames from the American population, or the relevant country - and in the same way DNA and the Y chromosome is passed from generation to generation, so are surnames. So by generating a link between the specific inherited marker and the surname, the door opens up.
Using this technique the Y chromosome can be taken from evidence left at a murder scene, or from DNA deposited on the seal of an envelope, entered into the system and a potential surname is presented to the observer. This technique can therefore provide the police immediately the name of potential suspects, vastly narrowing the field of investigation, coupled with the location of the likely perpetrator, making the job of apprehending a killer far easier.
The rarer the surname, the easier this technique becomes to secure a match with over a 75% probability, but the probability reduces as the surname becomes more prevalent (so a preferred suspect would not be called Smith). This forensic advancement used in the Zodiac Killer case could shake the murderer's family tree to its roots and literally drop the killer's name directly into the palms of our hands.