Douglas Bruster, a professor at the University of Texas, utilized analysis of Shakespeare's handwriting to determine if he authored the 325 lines in the 1602 quarto edition of The Spanish Tragedy.

His findings, which will be published in the September issue of the journal Notes and Queries, argue that some aspects of the writing, including text that people say does not follow Shakespeare's style, may be credited to print shops misreading Shakespeare's handwriting.

The idea that Shakespeare wrote the Additional Passages was first brought up in 1833 by Samuel Taylor Coleridge. The claim has long been unpopular.

If accepted, the Additional Passages would become the first largely undisputed new addition to the canon since Shakespeare's contributions to "Edward III" began appearing in scholarly editions in the mid-1990s. 

"We don't have any absolute proof, but this is as close as you can get," Eric Rasmussen, a professor at the University of Nevada, Reno, and an editor, with Jonathan Bate, of the Royal Shakespeare Company's edition of the complete Shakespeare, told the New York Times. "I think we can now say with some authority that, yes, this is Shakespeare. It has his fingerprints all over it." Elizabethan Theatre was very collaborative, and playwrights often revised older works or worked with other dramatists to create new ones.

Rasmussen and Bate are including The Spanish Tragedy in the Royal Shakespeare Company's new edition of Shakespeare's collaboratively authored plays, to be published in November.