The complex issues in the “reverse racism” appeal of a murder conviction are “wearing down” a Brooklyn judge who said Monday she is finally ready to render her decision.

But her ruling on the appeal of Donald Kagan, 40 — the white man whose 1999 murder conviction for killing a black man was thrown into doubt last year when the judge who found him guilty said he based his verdict on his own reverse racism — won’t be revealed until Kagan can be produced in court next week.

“It’s a complicated case. It’s one of those heart-wrenching cases,” acting Brooklyn Supreme Court judge ShawnDya Simpson told The Post after she adjourned the case.

“This one has really been wearing me down. I’ve been reading and reading and reading.”

The judge said that she had already written her decision.

“I’m done. I just want him here,” Simpson said during a brief court hearing, referring to Kagan. “I had no idea the defendant wasn’t going to be here today.”

As The Post first reported, retired Brooklyn Supreme Court Judge Frank Barbaro, 86, testified last December that he wanted Kagan to be freed because he based his verdict in the non-jury trial on his own anti-white prejudice.

“Mr. Kagan had no intent to kill that man . . . I believe now that I was seeing this young white fellow as a bigot, as someone who assassinated an African-American,” Barbaro testified.

Simpson adjourned the case until Oct. 1, at which point she’ll reveal her decision on whether she’ll overturn Kagan’s conviction, grant him a new trial, or reject his appeal and leave him to the mercy of the parole board.

Kagan is eligible for parole in November.