A crazed homeless man accused of fatally beating a good Samaritan who came to the aid of a neighbor should have stayed off the witness stand.

A Queens jury yesterday found Eric Cherry, 47, guilty of manslaughter and assault in the death of Nicolas Nowillo, 65, who suffered a heart attack as he was attacked outside his Astoria home Sept. 3, 2008.

One juror leaving the courthouse after the verdict was overheard telling Cherry’s lawyer, Steven Goldenberg, that his client “shouldn’t have testified.’’

Cherry had testified in his own defense that Nowillo spewed racial slurs and jumped on his back like a “spider monkey.”