Frank Edwards' book Strange World documented the story about "The Robber's Grave," and when the book was written the grave was still not replenished with grass. The tale goes like this, a young man named John Davies was wrongfully executed and the highwaymen that actually committed the crime got out free. So before John was executed, he told the crowd that to prove his innocence, God will not let grass grow there for 100 years. Of course nobody even believed that story but it did happen according to historical accounts, the grave was barren for at least a half of a century.
This happened in the Welsh town of Montgomery and now there is grass growing on his grave (as you see in the photo) which probably means that his soul could finally be at rest. The story is interesting because this isn't the first account of someone wrongfully executed and prove their innocence in extraordinary ways.
No doubt there is skepticism in people's minds but here is one thing to consider, in 1851 the whole graveyard was remodeled and the place was covered with two feet of fresh soil and grass seed but still the area would not grow around John Davies. It wasn't long enough obviously, so anyway that is the story of the tale of how one man got his innocence prove beyond the grave!
BBC: Mid Wales Montgomery