Accused "Son of Sam" murderer David Berkowitz is mentally unfit to stand trial but is "well aware of the charges against him" and understands that his alleged actions were criminal, a psychiatric report disclosed today.

The report is the same one delivered in Brooklyn Supreme Court on Tuesday, but details of the eight-page document were released for the first time as Queen District Attorney John Santucci read portions into the record at a competency hearing in Queens Supreme Court.

During the hearing, two phone threats were made against chief defense counsel Mark Heller, one saying he would be shot and the other a bomb threat. The three defense attorneys were later taken from the court-house without incident.

The report said Berkowitz "understands that by society's standars what he did is illegal" but "feels so emotionally dead that the outcome of this case is totally immaterial to him."

The psychiatrists concluded that "said defendant, as a result of mental disease or defect, lacks the capacity to understand the proceeding against him or to assist in his own defense."

The suspect in the six killings must undergo official competency hearings in Brooklyn, Queen and the Bronx - the three jurisdiction of the "Son of Sam" murders - and could conceivably be judged fit to stand trial in one county and unfit in another.

Meanwhile, Berkowitz has invited Daily News columnist Jimmy Breslin to "come over to my home at Kings County Hospital."

The newspaper said it received the letter late last week and released it after confirming that the author was Berkowitz.

Breslin said he would accept the invitation "at an appropriate time." However, Ira Jultak, one of Berkowitz' attorneys, said he understood that fellow defense counsel Heller had blocked the visit.

he undated letter, which the Daily Newes reproduced on its front page today:

"Dear Mr. Breslin,

"It has come to my attention that you wish to speak to me. Well, all you have to do is come over to my home at Kings County Hospital. At this time I am unable to visit you.

"I am quite disgusted with the way the press has been spreading lies about me but perhaps some of these can be ironed out in our meeting.

"However, I am not one to cry out a case of injustice.

"I hope Mayor Beame enjoys dribbling my head across the court. This is really like a circus event with clowns and criminals. Please bring a beer when you come.

"Sincerely, David Berkowitz."