LI Serial Killer -- Cop?

It appears some NY authorities think the LI serial killer may have some law enforcement background, maybe he’s a former cop, etc. It seems like I have heard this idea before on various fictional crime tv shows, books, etc., that the bad cop uses his knowledge of law enforcement procedures to thwart the investigation and avoid capture. My question is, does anyone know of an actual serial killer that was ever a police officer of some sort, either active or retired? Security guards don’t count!

Gerard Schaefer: Gerard John Schaefer - Wikipedia

They weren’t your stereotypical psychopathic serial killers, but Louis Eppolito and Stephen Caracappa were mob hitmen who were also cops: Stephen Caracappa and Louis Eppolito - Wikipedia

Not quite serial as far as we know, but CHP Trooper Craig Peyer beat and strangled a female motorist to death and was known to have harassed several others.

Flordia State Trooper Tim Harris is currently serving a life sentence for the rape and strangulation death of another female motorist. He was seen by his estranged wife wearing the victim’s underwear. The story can be found in the book You Belong to Me by Ann Rule.

David Middleton.

Isn’t there a cop in custody who is believed to have killed all three of his wives?

Not a cop but Timothy Krajcir got a degree in administrative justice, which apparently would have given him a lot of knowledge about police procedure. He had already been convicted of rape before enrolling so he never could have joined law enforcement.
Sorry it’s vague, but I seem to remember reading of a few cases where the killer was discovered to have applied to or attended police academy but either never got accepted or was deemed unfit for the department.

John Christiewas a special constable.

I have to say that when I read that article a couple of days ago, I didn’t think the evidence given necessarily pointed to any very specific knowledge of police procedures. I mean, I rarely read/watch crime oriented entertainment, and even I would know to call the hookers with a prepaid cellphone, and to keep traceable calls short. Those have been plot points in way too many movies at this point. (I will admit that making the traceable calls from Times Square and similar places is smart, and would be less obvious to me.) Perhaps there’s more evidence that the police aren’t releasing to the public.

You might be thinking of now-ex-cop Drew Peterson, whose fourth wife (Stacy Peterson) disappeared mysteriously, and whose third wife (Kathleen Savio) was judged to have drowned in a bathtub - waterless when discovered. Further examination of the Savio death suggests a struggle may have been involved. They were divorced at the time, but there was ongoing conflict (and numerous police calls) due to child custody issues.

For the Stacy Peterson incident, Drew’s stepbrother helped him carry a heavy, large plastic blue barrel out of the house soon after her disappearance, and this was seen by neighbors as well. The stepbrother states he thinks he might have unwittingly helped dispose of her body.

Oh, and his first and second wives are still alive, though the second one alleges he was physically abusive.

I agree. It’s not impossible the guy’s a cop or has police training but it’s not the only way he could know this. You could pick this stuff up from plenty of movies or TV shows or books or websites if you were interested in how police work.

Not quite what the OP is looking for, but there’s the recent Canadian case of Col. Russell Williams. By day, he was the Commanding Officer of Canada’s largest airforce base. By night, he was a lingerie thief with a fetish, a rapist, and a murderer.

One of the women he killed worked on the base, so the police routinely kept him informed of the progress of their investigation, since he was the CO. So you have a serial murderer being regularly kept informed of the police’s attempts to catch him, by the police themselves: Accused Colonel kept tabs on police probe:

Not a murderer, but a bank robber:

Timed the robberies when there were few cops on duty to give more time to escape, and also had access to police radio communication.

ETA, read that link, seems he might be a murderer too.

I was saying the same thing before I read the thread. I have seen nothing that would suggest knowledge deeper than anyone can get from TV. Of course I’m sure there is information they are not sharing publically.

Oh, if we can cite crimes other than murder, there was an attempt to blackmail Heinzby putting poison in jars of baby food.

It turned out that the perpetrator wasa senior policeman, who was part of the team investigating the crime. He was able to avoid arrest for a time because of his inside knowledge of the investigation.

This one is was not only a cop but female and the story is worse than it reads on Wikipedia. Antoinette Frank was a New Orleans police officer that helped orchestrate and conducted the killings of the Vietnamese family that she was doing restaurant detail for as well as her own partner. She might have gotten away with it but she didn’t realize there was another child there who hid in a cooler until it was over who saw the whole thing. She was linked to several other killings as well through forensic evidence. However, she got the death penalty for these murders so it wasn’t worth it to pursue the others aggressively.