In David Wroblewski's best selling novel The Story of Edgar Sawtell, a great deal of evidence shows us that the suspicions 14-year-old protagonist Edgar had all along concerning his uncle Claude's responsibility in the death of Gar, Edgar's father, were correct.
One point of evidence we have confirming Edgar's suspicions that Claude murdered Edgar's father and Claude's own brother, Gar, is the night the ghost of Gar visits Edgar on a dark and rainy night, soon after Gar's death. The ghost of Gar walks out into the rain from the barn towards Edgar "with [a] syringe in his hand," holding it out to Edgar. Through encountering the ghost of his father, Edgar comes to understand that the syringe was found under the staircase, that Claude has access to syringes through working with Dr. Papineau in his veterinary clinic, and Claude used the syringe to kill Gar.
As in Shakespeare's Hamlet, a play Wroblewski drew inspiration from for the novel, a second piece of evidence pointing to Claude's guilt in murdering Gar is seen when Edgar trains his dogs to reenact the murder as a dramatic play. When Edgar sees Claude's reaction to the play, he feels convinced of Claude's guilt.
Finally, the ending of the story is also a huge clue that Claude is the guilty party. Edgar returns home to find evidence against Claude when a fire is accidentally started. While trying to gather files he knows contain evidence of the lethal injection, Edgar becomes Claude's next victim.