If this guy has been a suspect from long ago why havn't they gotten a dna sample from him a lot earlier.
I know investigators can collect items from of a person's garbage or they can be put under surveillance and collect a discarded cigarette or coffee cup from a person without them knowing. I forget what they call it but I've seen it on forensic files many times.
Also I've read that there was a murder two doors down from this guy, so why wasn't he on the radar screen a lot sooner or why havn't they made a connection between him and many of the murder victims.
That took a relatively new technology - the polymerase chain reaction -- to be able to jump start it.
Think of the PCR as being like a photocopier. It makes thousands of exact copies of any strand of DNA. Theoretically, with PCR, you could take a single strand of DNA and make enough to test for a match. In reality, I think they need 20 or so now for it to reliably "take." Before PCR, when the major technology for testing DNA was restriction fragment length polymorphisms (RFLP's, which was current when I was in high school in 1999, I think), you needed a lot more DNA to test. Now, with modern PCR-analyisis, they only need a little bit.
"If this guy has been a suspect from long ago why havn't they gotten a dna sample from him a lot earlier."
Because he was not a suspect until recently.
I have been following this case for more than a couple decades. The one thing that BTK was very good at was making sure that the possibilities of who did it were in the thousands.
There was a lot of speculation for a lot of years that he may have even been one of the people investigating the murders, because he always seemed to be one step ahead of the police.
He did a very good job at making sure the fingers did not point to him.