"You may borrow the book, if you like," Clowers said to River, "It's rather basic, but I've found it helpful, though don't ask to see my paintings!" He laughed, "I've only started recently. 

"Now, to the subject at hand," he sat forward, showing a great deal of interest. "This is an excellent topic for a paper, a lot of people, especially young people, are more interested in a duel or combat itself; magical forensics is a sorely undervalued subject. First you must look at what evidence a duel, or indeed any crime, would leave at all. The damage caused by spells is an obvious problem, and far trickier than one might think. Many curses, especially the more powerful ones dark wizards are like to employ, cause damage that cannot be repaired. The most famous example is of course the scar that Lord Voldemort left on Harry Potter in his attempted murder. 

"This difficulty, or even impossibility of hiding or repairing the damage extends not only to injured beings, but often inanimate objects as well. So. If you cannot hide the fact that a duel has taken place, or a spell cast, where does this leave us?"

Richard, distracted by Clowers' painting bench, did not answer.