Shooting Lincoln

[richard petersen]

In today's WSJ on page c10 there is a review of this book written by Nicholas J.C. Pistor.
The book is about the rivalry of photographers Gardner and Brady. At the end of the review it states "during Mary Surratt's trial, prosecutors revealed she had kept a photograph of JWB hidden at her boarding house. The revelation all but convicted her"
Did the above comment take place and have consequences at the trial?
The review was written by Harold Holzer who authored "Lincoln and the power of the press.