Tried search terms: Excessive force, overkill, extenuating circumstances, FBI Internal Affairs, criminal trial, criminal process, self-defense.
Hi peeps, I was hoping someone could help me figure out a part of a plot that I've been struggling with.
The plot involves a character who works as some form of support staff/consultant/informant for the FBI (not a special agent). He works in a completely fictional and recently-created response team within the FBI that investigates an increasing amount of experimental medical drugs being distributed through tainted illegal drugs. The character gets kidnapped by a gang leader who has been suspected of breaking into research facilities and stealing experimental drugs and selling them on. The SSA of the team knows of the gang leader's involvement, but has kept it a secret from the character, since the character in question has very traumatic memories of said gang leader killing his mum and abducting him as a child (something that was for various reasons never in any official records). The character suffers from mental illness related to this and the SSA keeps him in the dark about the situation to protect him.
The character is held kidnapped and beaten for a few days before he manages to escape. In his escape he kills several gang members in what can be considered clear self-defence, but he also kills the gang leader in self-defence and this is where it gets tricky. The character doesn't realize the gang leader is dead and therefore continues with what he's doing in the belief that he's protecting himself, due to a mix of PTSD and rage. This involves impaling the gang leaders hands to the underlying floor with a knife, which is connected to sexual abuse that the character suffered at his hands. After escaping, he keeps away from law enforcement for a few days before he's forced to seek medical attention due to the injuries he has sustained (gunshot wounds from the escape and being beaten while he was held against his will).
I can't figure out how this would realistically be investigated. Law enforcement knows he was kidnapped and had a threat to his life and the gang members' deaths will be ruled as self-defence, but I don't know how the FBI or the police would respond to the overkill of the gang leader. Would that be investigated by Internal Affairs or would he have to go through a criminal trial? If it's IA, would the investigation be in any way similar to a criminal trial? If it's a criminal trial, what would happen if he admitted to killing the gang leader and using excessive force but argues it was extenuating circumstances at the hearing? Remember that there's no official records proving that the gang leader had killed the character's mum and abducted him as a child, although I have planned for evidence of this to come to light later on during the investigation.
I like the drama of a criminal trial, but in real life they seem to take so much time and I would like to wrap up the story-line within less than a year from the kidnapping. I have tried to read up on the FBI and the US justice system, but it's not easy since I have spent less than a month in total in the US in my entire life and never in Washington DC. I'm open to bending the rules a little bit or changing parts of the story, but I'd like it to seem at least a bit realistic. Any help is appreciated!!