I've been reading mysteries since I was twelve starting with Nancy Drew and the Hardy Boys. I always enjoy seeing if I can figure out the whodunit or what happened before the book reveals the true identity or event. But over the years I have to say there are some sleuths-amateur and professional alike- who have made me scratch my head.
I don't know about you but I have trouble with some solving, say a murder, and they have the TSTBA syndrome. You know- To Stupid To Be Alive. Why would they burst into a place they believe the killer is? Or take off not telling anyone where they're going when they are following the person they believe killed Aunt Gertie. There are some authors who use that with their sleuth so much I guess the reader becomes numb to the stupidity of the character's actions.
Or there is the mystery that looks like it could be one of three people and the last third of the book some new person is brought in and they turn out to be the killer. That's just not fair in my estimation. Not when I've been reading along putting the clues together and trying to beat the sleuth to the answer. When an unknown entity is brought in out of the blue that ruins the book for me. There has to have been some mention at least twice before that doesn't leave the reader wondering there the heck that person came from.
For me a good sleuth has to have common sense, some element of their personality that won't let them allow an injustice to happen(the wrong person being accused), and a unique way of discovering the clues. Like knowing human nature and watching and listening, having a high intelligence to decipher the clues, or a high curiosity. To me the characters who are solving the crimes for reasons other than money make the best stories. They are striving for justice and that makes their reasons more compelling to me.
What makes a good sleuth for you and why?