Conversation so far:
Who is william Hope?
the spirit photographer William Hope was a fraud.
How was he a fraud?
William Hope has been found guilty of deliberately substituting his own plates for those of a sitter ...
Why did William do this?
CANNOTANSWER.
How did people percieve him?
Doyle threatened to have Price evicted from his laboratory.

Question: Why did he do this?
Self-contained rewrite: Why did Doyle threaten to evict Prince?