I was reading about the BTK Killer and it said that he sent a copy to the police. The police were able to find out it was made on a Xerox machine. And the cops sent the copy to the Xerox headquarters and they were able to trace the copy to the exact machine in Wichita. They also said they were able to tell it’s a fifth generation copy.
I’ve also read two more cases were the police were able to able to trace the copy made to a particular machine. All three times the copies were made on Xerox copy machines.
So first of all am I correct in saying Xerox must be putting some sort of near invisible code on each copy you make? Like a really small one or two pixels?
Secondly if this is true, then would all makers of copiers put codes on things you copy?
And last by a fifth generation copy do they mean it was copied five times prior?
FWIW, all of our color copiers at work produce a visible thin yellow line across every printed page that identify the source of the copy. Updated article from EFF that confirms the above 2005 article.
Mr Bathsheba, who was a Xerox employee for fifteen years, assures me that colour copiers were only introduced in c 1990, a bit late for the BTK killer. Also, at that time, there was no technology to do the encoding type stuff linked to in the article. However, the Xerox lab would be able to tell where the copy came from by analysing the toner used. Toner composition was/is tested each day and they kept/still keep records of what batch of toner went where, probably up to and including individual bottles.
For some odd reason the BTK killer sent the notes in 2004 along with other stuff. They didn’t even realize the person he killed in the mid 80s was killed by him till he sent the note. He didn’t kill between 91 and 2004
