What was the Name of Sunday night show about witness protection program on tnt that aired in summer 2008?

The show you're thinking of is called "The Closer". It aired on TNT, and while it wasn't specifically about the witness protection program, it did frequently deal with cases involving the program, as well as other forms of undercover work and crime.

The show ran from 2005 to 2012, and the summer of 2008 would have fallen within its run.