When Sheriff McAllister saves Patrick on the roof (Season 6 Episode 3), he helps him up with his left hand, indicating that he is left handed. When Red John is choking Kira Tinsley, he uses his left hand, indicating that he, also is left handed.

10% of people are left handed
There are 5 suspects remaining on the list

Do the maths for yourselves. Thomas McAllister is Red John :D