“If the characters only serve the plot requirements, then one may discover that they lose their verisimilitude.”
There are lots of suggestions about writing the perfect crime story or the perfect best-selling novel for that matter.
I take all suggestions with a pinch of salt and, over the years, I found that “write every day” is the only advice a writer needs. From there she will go on to discover what works for her and, if it’s fate, even go on to writer her best-selling novel.
For all the others, who are still interesting in advise and suggestions, here’s another article about it.
Happy reading, but most importantly, happy writing.