Natalee Holloway

Natalee Holloway's brother has serious doubts Joran van der Sloot has found God after killing his sister ... and he's ready to hand the murdering monster a beatdown if he ever walks free.

We also talked with Matt about why he thought it was practically impossible to nail van der Sloot for Natalee's killing all those years ago -- and he feels van der Sloot's father being a high-profile attorney in Aruba interfered in the investigation.