Homicidal ideation

I know your thread is a bit old, but FWIW, I'm dealing with a similar situation. On one hand, I want to be clear on my need for therapy, but, on the other hand, I can see it not playing out in my favor, e.g.:

1) Being reported to authorities, put on a watch list, etc
2) Being involuntarily commitment or even briefly retained
3) Having this on a record somewhere, in case it ever surfaced, for whatever reason

I go back and forth with revealing the full truth or just the more tame parts of it.

If you know you would never act on your urges, it doesn't seem like you have much to worry about. From what I've read, homicidal idealization without intent isn't all that uncommon, and as long as your moral inhibitions are intact, an ethical therapist wouldn't violate your confidentiality.

That being said, therapists are human and are not inherently ethical. Additionally, depending on how you frame discussions of your "fetish" and any possibly contributing issues your therapist might already know about, they may just go on their judgment to decide whether they think you're a real threat, regardless of what you say. I had a therapist tell me once that they were required to report suicide/homicide intent, but most patients would just say they weren't suicidal, and then go do it anyway. I'm not sure if that was to imply that he'd have to make a judgment based more on his overall impression than the specifics, or more of his way of saying don't ask, don't tell.

My personal approach would be to ask, directly, how the possible answer to certain questions could potentially impact confidentiality. This certainly implies that you're considering hiding something, but gives you plenty of opportunity to understand what you're willing to reveal.

Read the rest of the thread now, and if you've already discussed biastophilia, necrophilia, and necromutilomania, homicidal ideation goes without saying. I mean, you attack them, hurt them, rape them, have sex with their dead body and mutilate their corpse. At the beginning of that, they're upright, happy, and alive, and at the end, they're dead and mutilated. There's a logical gap in the story-line there, and murder is the obvious filler.

If your therapist is at all surprised by homocidal ideation, you have the wrong therapist.

If you know you are not strong enough, but do not want to tell her. If you just want to, then I would not recommend. I personally have been to avoid ever having to a therapist, but your past that stage. The most important project, your decision, do not do anything rash, you may regret it.