Brooklyn District Attorney Ken Thompson is set to drop charges Friday against a dad accused of extorting an alleged pervert, the father’s lawyer said.

In the 3-year-old case, which illustrates the friction between Thompson and predecessor Charles Hynes, Sam Kellner, 52, was charged with extorting Baruch Lebovits, who was accused of groping Kellner’s son.

“It’s going to be dismissed,” Kellner’s attorney, Niall MacGiollabhui, said Thursday night.

“Prosecutors will tell the court neither of the two witnesses [against Kellner] are credible.”

During the 2013 election, Thompson called the case “botched,” while Hynes stood solidly behind the prosecution.

A DA spokeswoman did not provide a comment.