There was Dr.Wood there to help me.

We found no signs of violence upon it.

I was hoping that if Mr.Douglas defended himself with the hammer, he might have left his mark upon the murderer before he dropped it on the mat.

But there was no stain." "That, of course, proves nothing at all," remarked Inspector MacDonald.
"There has been many a hammer murder and no trace on the hammer." "Quite so.

It doesn't prove it wasn't used.