Did the writers know from the beginning who Red John was?

Question

Rewatching The Mentalist lately, I realized that we actually meet Red John quite early.

The true identity of Red John was revealed years later.

That made me wonder. Did the writers know the identity of Red John from the beginning or was it decided later in the show?

Answer 1

Doesn't look like it, according to series creator/exec producer Bruno Heller in November 2013:

"Xander is a wonderfully subtle actor who can go deep — deep enough to be our Red John," says series creator/exec producer Bruno Heller, who says he selected McAllister to be his Big Bad "about a year ago, after carefully weighing all other options. McAllister made the most sense. He had the perfect cover job as the sheriff of Napa, where he was the master of his domain. No one ever questioned his whereabouts. He didn't have to answer to anyone. He needed that freedom and the quiet loneliness of the countryside to do his thing as Red John."

More from Bruno Heller in The Hollywood Reporter (also November 2013):

It was important to "give a real emotional, pleasing end to that story," creator-showrunner Bruno Heller told reporters, admitting that the ultimate Red John identity slowly "emerged" over the last few seasons. "For me it was about giving Patrick Jane exactly what he's wanted for all these years. He wanted revenge and he got it. I think that's what the audience wanted, so that's what we gave them."

In Entertainment Weekly (November 2013):

When did Heller decide Red John’s identity?

Bruno Heller: I’m not sure. It kind of just emerged over the last couple years. There was always three or four possibilities. And it just happened, really. It seemed like the natural correct choice.