It's nice to live in a place where there is some honest uberauthority which will guard your interests. If you are trusting the fbi in that regard you probably have not been following the news for many years, or you have not been reading with a critical mind.
The fbi does not come from 'some other area'. They were not segregated so that the fbi lived on one side of the island and locals on the other.
Throughout the whole time that Burke was operating alongside lots of other corrupt figures the fbi got report after report, complaint after complaint for year after year.
You can argue why the fbi ignored the corruption there for so long, but saying they were not aware of it is ludicrous.
And the fact that they were utterly absent morally until publicity forced them to get involved does not give them extra weight.
Those who have followed similar scenarios in various locations over the decades know how it goes. The fbi will make the minimum possible number of arrests of corrupt officials. Then a fixer comes in, Hank Schuelke is my favorite, and all of a sudden everything is explained.
I would bet heavily on the fbi assisting the Suffolk police in not producing adequate documentation of the dna, and anything else the Suffolk police need help with.
It isn't a 'conspiracy theory', it's just the truth.
You've made your wacky interpretation of this case plenty apparent on previous pages of this thread, and I can't tell you how disinterested I am. Let's move on..