Your victim was ...
... a Mockingbird.
Whenever I need something investigated, I always turn to a 1990s dance artist.
In his side career as Private Invistigator, the dance artist in question was the Moby Dick.
I have no problem travelling to the Free State, but will refuse to go further south under any circumstances. Also, I once fainted in the movie theatre while watching Superman Returns.
Someone who is afraid to go to the Southern provinces of South Africa or who is frightened by Superman's attire suffers from Cape Fear.
I am not completely against illicit narcotics, but will refuse to take them in the afternoon. Or in the morning. If you want to take drugs with me, midnight is the right time.
In other words, I'm on a Twelve O'Clock High.
I have known both Neymar and Ronaldinho when they were only children.
They were then known as the Boys From Brazil.
Perhaps most famously, I once plotted to murder [censored]
The above are all films starring Gregory Peck, who famously played the Attorney Atticus Finch in To Kill A Mockingbird.
What does any of this have to do with chickens?
Well, chickens peck.
The first thing I got was clue #2, but I used the Cape Fear Remake with Robert de Niro istead, who starred in Analyze This, Midnight Run, Brazil. My proposed overall answer was the not overly convincing Killing Season. (But it was convincing enough to get me 12 upvotes.)