Name of movie from the 1950-60s?

BS"D
I'm hoping someone will see the description of this movie and remember the name. I saw it when I was very young, broadcast on TV and, if I'm not mistaken in b/w. It was about a woman who was sentenced to death for murder. Thereafter she was found innocent. I remember my father o.b.m. discussing the movie with me after we had watched it and he told me it was based on a true story. Nearly 50 years later, I am still haunted by what I saw. For some reason, I remember a scene with white chalk writing on a blackboard. That could have been the opening scene/title. Any movie buffs out there who might be able to tell me the name of the movie or the actress? Thanks, in advance.