Setting: Modern day California (specifically, the fictional Beacon Hills, as this is Teen Wolf fanfic)
Searched: I'm not really sure how to search for answers to any of this.
Short Version: To law enforcement (FBI, namely), several teenagers have confessed to inducing a severe deterioration in a man's pre-existing cancer, but they also claim this man was severely abusing them, and had prevented legal recourse via a combination of intimidation and eliminating evidence. There is absolutely no physical evidence of any of this - neither the teens' assault/medical manipulation, nor the abuse. But there is a lot of circumstantial evidence. The man himself is dead, having recently been found murdered by his own daughter (a known/convicted serial killer). The man's surviving family members all claim, to varying degrees, that he was physically abusive at home, but again, there is no evidence of any of this.
Would these teenagers be charged with any kind of crime? How would law enforcement handle/react to this? Is it plausible that they wouldn't bother pursuing the case due to lack of evidence?
Additionally, from the perspective of law enforcement, this town has been subject to some kind of "serial killer competition" (their current theory, as to them, there have been multiple serial killers in a very short time frame and in this one town/area - they don't know this is a supernatural warzone, since the supernatural world is still hidden from the "Muggle" world in this universe). Would the official response/perspective been in any way impacted by the fact that a.) the man is already known as the father of one serial killer and is loosely connected to another (one who killed five cops), and b.) these teenagers have all been recurring attempted targets/been targeted by multiple serial killers several times?
[Long Version Behind Spoiler Tag]The teenagers claim the man wan was abusing them somehow (psychological? sexual? whatever it takes), and their claims are backed up by the man's son and granddaughter testifying to the fact he was physically abusive at home. The man's daughter is already a known psychopath - she was posthumously convicted of murdering nearly two dozen people in two separate killing sprees. She has recently been discovered to be alive after all, and she has been recorded as confessing to murdering her father and called him a monster, but she escaped police custody before anyone can make her explain what she means.
The teenagers also claim this man was the driving force behind two separate serial killers/was somehow working with them (one of them being his own daughter, the other being another teenager who murdered five of the cops along with several townspeople). On top of that, they claim suspicion that this man murdered his daughter-in-law (whose death was framed and ruled as a suicide at the time). The man's son and granddaughter are also willing to claim/testify that this man was physically and emotionally abusive at home.
All of this, however, is based entirely on everyone's word, because there is absolutely no physical evidence of any of this - neither the teenagers inducing the downturn in the man's cancer, nor the abuse they are claiming this man committed. The closest thing to evidence is a.) some nasty scars that the son and granddaughter can claim he inflicted, and b.) evidence that missing footage from the school's security cameras was actually deleted during his brief term as a volunteer principal for the high school these teenagers attend, and not just lost to technical difficulties like he claimed.
For those who are familiar with the Teen Wolf fandom or just want names to attach to these characters: I'm playing around with a Season 4 AU in which Allison, the granddaughter, is still alive and around, as are Erica, Boyd, and Jackson. Kate (the man's daughter, and known serial killer) murdered the man (her father, Gerard). Rafael (the FBI agent who can be seen as representing law enforcement, here) has, due to story shenanigans, twigged onto the fact this group of teenagers was involved with the man well before his death. Scott (the FBI agent's son) is hoping to get ahead of the investigation and throw off suspicion from even bigger/more convoluted problems going on at this time by everyone confessing to and claiming all of this, thereby distracting Rafael, the FBI, and the police.
Scott, Allison, and Stiles (the town Sheriff's son, and also a victim of Gerard) claim to have done this to Gerard because he was abusing them, as well as their friends Jackson, Erica, Boyd. Another teenager, Lydia, was being severely psychologically abused at the time, just not by Gerard - she was brutally attacked by a mysterious man she didn't see clearly, losing long periods of time, and had injuries she did not remember getting - and there is documentation of these. Her assailant was never found, but her problems did mysteriously stop at the same time that Gerard's cancer took its mysterious downturn. His cancer took its mysterious downturn the same night that one teenager was stabbed and another severely beaten, both also by unknown assailants. Additionally, the man's daughter did statutorily rape someone: Derek, whose family she was convicted of murdering several years ago when he was a teenager. He is now coming forward about it as a warning since it turns out she's alive after all, and he did this independently of Gerard's murder case. Yet again, no evidence, but this time only because the relationship happened seven years ago, not for supernatural reasons.
What kind of reaction can I expect/plausibly write from the FBI? And the local/county police? Is there anyway for there to be a legal record of all these claims and confessions without anyone going to prison, or should I just stick to the kids not saying anything about any of this to anyone involved in law enforcement? (I'm aiming for there to be legal records of all of this for story reasons down the road, but if it's not possible, I'll make do without it).