Wald's wife would not testify against him (and contrary to popular superstition she could if she wanted to), claiming she had "blacked out." So the only established fact is that Wald shot a man who, he says he believed, had invaded his home and was assaulting his wife.
Which I believe is justifiable homicide in just about every state. Whether it happened that way, who knows? However, juries are required to give defendants the benefit of reasonable doubt.