Robert Durst's prosecutor went nuts on his prey Friday ... saying he's just a killer by nature.
Durst looked feeble in his wheelchair as Deputy D.A. John Lewin unleashed his fury on the famous defendant.
The hearing itself was kind of boring ... just about witness lists. But the tone is what got us.
Durst has already won a murder case against a seasoned prosecutor, and it's clear Lewin is not about to be victim #2.