How many books do you have planned for your Helen Binney series? Can I ask a question in advance to have something to look forward to when I read it? Who is your favorite character in the book?
At the moment, it's three books: A Dose of Death, A Dash of Death and A Deal of Death. Second one is in second draft (of three), and third one just has a vague premise.
For a favorite character, I honestly don't have one. Something I learned from reading Terry Pratchett, and that I try to put into effect when I write, is how important it is to love all my characters, even the killer, even the annoying soon-to-be-corpse. (Someone once pointed out to me just how much Terry Pratchett seems to love all his characters, so even when he's making fun of someone, like the Igors with their lisps, it doesn't come across as mean, but as coming from a place of love.) I don't know who first said it, but every character is the protagonist in his/her head, and it helps to remember that when it comes to making them well-rounded.
And that also explains how I approach creating characters. I start with knowing the role they need to play in the mystery or its investigation (because I do a lot of pre-writing and outlining), and then give them some small trait (positive or negative) that I myself possess (because we're all narcissists to some degree, so it helps me to bond with the character), sort of like how therapists say that everyone in our dreams is some facet of ourselves, and after that, much as my logical legal brain hates to admit it, how the characters come to life is kind of just magic. I can't explain it. They just start talking, and I know who they are from what they say and do.
One thing I don't do is character sheets (in advance of writing; I create a cast list as I write); they make me freeze. Way back when I first started writing fiction, I went to a conference where I was overwhelmed by how much I didn't know about writing, and the final straw was a workshop that purported to teach us how to create characters, and we were given a five-page hand-out of things every author needed to know about their protagonists. One of the first things on the list was "what jewelry does he/she wear," and I totally panicked, because I don't wear jewelry, never have, and the thought of even going into a jewelry store for research made me hyperventilate, and how the heck was I going to know that when I hadn't met the characters in action yet, which is where I found out who they were.
These days, I do have some characters who wear jewelry, but at the time, the idea of HAVING to know, right up front, before they'd introduced themselves to me in the story context, what their jewelry preferences were completely freaked me out. I stopped writing for at least a year. Seriously. It was painful. Don't let this happen to you!
Bottom line: however you create your characters, however you create your stories, if it works for you, then don't let anyone else tell you different. I do think it's good to hear how others do it so you can try different methods -- I started as an outliner, went to pantsing and came back to outlining, but using a variation on the snowflake method, rather than what I did at first, which was to go straight to the outline -- because you don't know what will work (and what will make you hyperventilate and stop writing) until you try it.
Oh, and just as an aside, one of the other series that I'm working on features a quilt appraiser who solves murders related to quilts. I'm not an appraiser, but I'm an award-winning quiltmaker with one quilt owned by the Museum of American Folk Art in NYC. My fabric stash can beat up anyone else's fabric stash.