I believe he is RJ.  During the season 1 episode 11 "Red John's Friends", Minelli took a 'vacation', and suddenly CBI gets communication from RJ?  How convenient.   Also, when Minelli left Rosalind after drinking tea, the figure of RJ looked like him.

Minelli knows how to charm older women, as he is middle aged himself.  His eyes, actually look quite evil.

Also, Bob Kirkland could be Lorelei Martin's brother, wanting to avenge her and his dead sister, since they all look hispanic.
Therefore he gave RJ's accomplice a death he could not fight off, painless but the fact that he couldn't stop him from injecting that substance must have felt great great vengeance. 

Also, BK asked: "Do you recognise my face?"  Because RJ's accomplice at the hospital knows Lorelei Martin, and her sister, but perhaps not the brother, him.

BK hates RJ.

Minelli is RJ.  He too shook hands with Patrick in a flashback episode in season 5.
Reed Smith, and the Sheriff? Oh come on, they were jus random cameo appearances.