Who is Cecil Aguillard and the Lafayette Sheriff from Heaven's Prisoners and what is their importance?

After Dave is assaulted by Eddie Keats and Toot, the Lafayette Parish sheriff visits the hospital to process forms. It becomes quickly apparent that the sheriff is not going to pursue much of anything. Later, Dave applies for a job with the sheriff's office and gets it. The sheriff appears to have brain damage because he knows Dave is on an alcoholic binge and is only interested in taking the job so he can get revenge on the men who murdered his wife. After Dave vanishes for a few days of quasi-legal activity, the sheriff assigns him a partner named Cecil Aguillard.