CS Lewis Web
The Lewis Legacy-Issue 69, Summer 1996
Analysing for Authorship with the Cusum Technique
By: Kathryn Lindskoog
The C.S. Lewis Foundation for Truth in Publishing
September 1, 1996

Andrew Morton, widely regarded as the world authority on authorship attribution, developed the cusum (or QSUM) technique in 1988 after 40 years of research. His method identifies authorship irrespective of genre, over long periods of time, and from an early age. Since 1990 it has been accepted in law courts as a sound identifier of disputed utterance, and has been employed in cases involving suicide letters, confessions, witness statements, anonymous calls, recorded conversations, plagiarism, and forgery.

This method is based on habitual, unconscious use by the writer/speaker of function words (such as a, the, of, in, and, but). It does not analyze literary style, literary quality, authorial intent, or authorial honesty. It is strictly a quantitative analysis of syntax.

The task could be undertaken with pen and paper and super-human patience. Once when Dr. Michael Farringdon presented cusum evidence in the Central Criminal Court, Dublin, the judge inquired, "You could do this using an abacus, couldn't you?" "Yes indeed, my Lord, but it would take a very long time...!"

Dr. Farringdon contributed "The Critics Answered," chapter 10 of Jill Farringdon's new book, Analysing For Authorship, which explains everything about Morton's method.

Jill Farringdon is a freelance writer and literary reviewer who also works as an authorship attribution consultant. Until 1985 she was a Lecturer in English Literature in Swansea. Her book includes cusum findings on writings of Helen Keller, Mark Twain, D.H. Lawrence, Muriel Spark, Tom Stoppard, Anthony Burgess, Henry Fielding, and both authors of The Federalist Papers, as well as the real writer of Diary of Gerald Keenan.

In England the book costs 35. The U.S. distributor is Paul & Company, Tel. 212-564-3730, Fax 212-971-7200. It is also available from J.M. Farringdon, Booksellers (usually antiquarian), priced at $60 post-free by air. Tel. or Fax +44-1792-405267.