The photo used for the character Heather Greco was Kim Poirier's professional headshot, it can be seen on her official site.
Curtis Caldwell Blake, on the phone, tells the one who hired him that he has even taken people out of witness protection before. Around 20,000 witnesses and their relatives have been guarded by U.S. Marshals since WITSEC started back in 1971. This programme possesses has a 100% success rate, such that no witness who followed all of the instructions given them by the U.S. Department of Justice has ever been murdered whilst under Witness Protection. Thus, nothing is said about any who did disobey, and therefore the contract killer's words could be true even in the real world.