To Outline or Not to Outline?

So, today I've been working on my new WIP. It got me thinking. . .Should my outline be more concise? Of course, I decided no. No way, because my novel is taking a turn of its own, where one character is screaming at me that HE should be the killer. Naturally, I've decided to let him pillage the village or however that saying goes. And, believe it or not, he's doing a pretty good job at being evil--though my MC doesn't know it's him yet.

The question is: When does outlining  a novel work?

Personally, I have to have a sense of what my story is and where it's going. If you're writing a mystery like me, then you know you have to have a good idea who the crime solver and killer are and who wins in the end. 

Of course, having a not-so-normal killer can be difficult. Take my novel for example. I had to have a good grasp on the ending, because, well, my killer can't exactly have handcuffs thrown on him. Nor can he live it up with a bunch of jailmates.

Yeah, that's why I needed a solid outline for this one(though I'm always up for revising it). In order to make something believable to others, I have to believe it myself. And, I can't do that if the ending doesn't flow and become feasible. 

The one thing I ALWAYS do, however, is the whole character sketching. Not right away, anyway. Then, I write a sample chapter where I let the characters interact, and generally, I am able to figure out their personalities from there and build on it.

That's just me though.