Creating a story

Having researched a selection of examples now, I'm starting to understand the structure of these types of films/series'. It seems that in most cases, there is always a protagonist character which you follow throughout the story, which for the most part would appear to be a detective of some sort. Alongside this, the opposite is that there's also a strong focus on the antagonist character too, which would be the criminal in this scenario. There is often equal importance in both roles as they go against one-another. 

I'm not looking to create a whole story just for a short title sequence, however I do feel it is important have a basic plot in place before developing any imagery or text. Since my topic of choice is True Crime Documentary series, it might be interesting to research an actual case to base it off. I've gathered here a small collection of cases together, outlining the key details from each of them before I develop my own story from them. Since the animation will obviously feature lots of imagery, I have also included some of the crime scene photos and articles of each case below in the hope they will inspire me to come up with a

Case of William Heirens;
William Heirens, also known as "The Lipstick Killer" was a serial killer responsible for three murders in 1946.
He maintained his innocence until his death in 2012, claiming he was the victim of an "abusive and overzealous" police force who were growing increasingly determined to pin the blame on somebody.
"The Lipstick Killer" alias came from the fact that at one of the victim's houses, the murderer had sprawled a chilling message across one of the walls in red lipstick. The message read "for heavens sake catch me before i kill more i cannot control myself".
Some images and articles from the case are featured below;

Case of Ricky McCormick;
The case of Ricky McCormick is an unsolved murder case in which his body was discovered in a field in 1999.
Several hand-written documents were found in the pockets of the victim, Ricky. Many organisations, including the FBI all come together to try and decode the messages, eventually turning to the public for help, however nothing ever came from it.
These are the messages below;

Case of the "Freeway Phantom";
The case of the "Freeway Phantom" is an epithet for an unknown serial killer known for six murders of black girls and teens in the early 1970's. 
In the pocket of one victim was found a note in which the killer dubbed himself the "Freeway Phantom". 
The killings only lasted 17 months before they abruptly stopped, however the case remains unsolved. The case was subject to such systemic racism that the original DNA samples and other evidence has since been lost as authorities cared significantly less about the victims purely because they were black.
Some images from the case file are featured below;