"OH, YOU CAN'T CHOP your poppa up in Massachusetts" (as the old song has it) and, after today, you won't be able to collect Social Security survivor benefits if you do. Sharp-eyed budget cutters in the Social Security administration have uncovered at least two cases, both in California, of young people who murdered their parents and then collected survivor benefits. In one case, a young man who killed both his mother and his sister when he was 15 years old received a lump sum of $21,500 upon leaving prison five years later.

The second case involved a boy of 14 who murdered his father and collected $8,000 in Social Security benefits. These cases give new vitality to the word chutzpah, a Yiddish term meaning, roughly, incredible nerve. Until now, the classic example ofchutzpah was the boy who killed his parents, then threw himself on the mercy of the courts, asking for leniency because he was an orphan. The California boys apparently weren't satisfied with mercy--they got cash. Your cash and our cash.

It is an old principle of Anglo-American jurisprudence that a wrongdoer should not be allowed to profit by his evil deed. Thus, life insurance proceeds are not paid to a beneficiary who is, in fact, the murderer of the insured. Similarly, a murderer cannot inherit under the will of his victim. Jean Harris lost not only her freedom, but also a large bequest in Dr. Herman Tarnower's will when she was convicted of his murder.

But while life insurers and executors were keeping an eye on police blotters around the country, Uncle Sam's computers just kept on writing checks. Federal regulations required a felony conviction before payments could be stopped, and juvenile court findings didn't meet this standard.

Social Security isn't sure how many more death- dealing dependents are collecting benefits, but they're checking their records. In a delicately worded directive from Washington, field officers have been advised not to process claims "from survivors who may have been involved in an intentional act which resulted in the death of a parent." Good. This is a loophole just waiting to be closed.