WE WON'T PRETEND to be shocked at the hawking of information about David Berkowitz. The selling of the "Son of Sam" story was perhaps inevitable. The suspect's neighbor, Sam Carr, with his daughter, a police dispatcher who had a role in the arrest of "Son of Sam," is reportedly offering interviews - for $15,000. The suspect's erstwhile sweetheart, now living in Michigan, sold two of his old letters for $500 and $200 each. Caveat emptor, we suppose.

But there is something more than familiar commercialism involved in the report that a lawyer, Phillip Peltz, who spoke extensively with David Berkowitz last week after his arrest, allegedly offered to sell his taped interview with him for $100,000 plus a percentage of the later book profits. The report, denied by Mr. Peltz, prompted a court order banning such a sale, but isn't known whether any similar offers were made to other media outlets prior to the court order. The New York State Supreme Court has ordered an investigation of the attorney's conduct. Clearly, one is needed. For despite Mr. Peltz's request on Monday to withdraw from the case, several questions still demand answers.

How did Mr. Peltz come to be David Berkowitz's attorney? In response to one questioner, Mr. Peltz said he was hired by the suspect himself - though it has yet to be determined if Mr. Verkowitz can be held responsible for his actions. But to another questioner Mr. Peltz said he was hired by a Berkowitz family member, whom he refused to name.

Then there's the matter of Mr. Peltz's conviction on four felony counts in a 1969 stock fraud case for providing a prostitute to a Securities and Exchange Commission official in return for information about a pending SEC investigation. Though he may yet face bar association disciplinary action, it is astonishing that this man, a convicted felon, has not already been disciplined. With this past, how did he come to represent one of the most hundred murder suspects in New York City history?

The head of the American Bar Association said the other day that Mr. Peltz's behavior seemed to be at the "edge of ehicality." The word is an odd one and it is not very clear to us what it meant by the "edge."