The Law School has added a documentary land-mark in American history--the first death-sentence laws of the Puritans, based on Old Testament texts--to its Treasure Room collection of rare American legal documents in the library, it was announced yesterday.

The historic document, presented by the West Publishing Company of St. Paul, Minn., is a copy of the earliest known tract of laws enacted by the Puritans. One of two known contemporary copies of the "Capital Lawes of Now-England," it was printed in London in 1642. The other known copy is in the British Museum.

These laws represent the Puritans' efforts to derive laws directly from Biblical authority without reference to English statutory or common law. Originally printed in Cambridge in 1642, they were reprinted in London in 1642, and it is one of the reprints that is now in the possession of the Law School.

Fifteen offenses punishable by death are listed in the document. In all but two cases Old Testament texts were cited as authority for each law, rather than the legislative and judicial authority of England.

The law deal with such diverse subjects as witchcraft, "worship of any other God but the Lord God," adultery, and "murther." They represent, says Perry G. E. Miller, professor of American Literature, "the most extreme effort of the Puritans to base their laws on the Bible and to get away from the common law of England."