EXCLUSIVE

Johnny Lewis -- the "Sons of Anarchy" star who murdered his landlady, dismembered her cat and then fell to his death in what appears to be a drug-fueled rage -- had deep ties to Scientology and its drug abuse program ... TMZ has learned.

We've learned Johnny's father, Michael Lewis, has reached one of the highest levels in the Church of Scientology. In fact, in the 80s Michael co-wrote a movie with L. Ron Hubbard about L.Ron's "discovery" of Dianetics.

Johnny was also active in the Church, especially the drug abuse program -- Narconon. In 2004, Johnny is seen (above) speaking at a substance abuse prevention event in the O.C. on behalf of Narconon. The reason Johnny spoke was because he was in a new show, "Quintuplets," and Scientology posted on its website that Johnny's mother used the principles of Narconon to keep him off drugs, and it worked.

Ironically, it didn't work because -- as we reported -- Johnny was in rehab this year (not Narconon) and eyewitnesses say he was clearly on drugs at the time of the murder.

Interestingly ... after we contacted Scientology about this story, they removed the photo of Johnny from all of their websites as well as the story about his appearance at the O.C. drug abuse event.