Solution to: Case 1: Every murderer makes a mistake

You:(Aggressively) Arrest the constable!
Assistants: Sir, but how did you find out?

You: Two reasons:

1. We all know that these 4 suspects were found in the locality, the one detail that we failed to notice is that even the constable was in rounds in the locality. So he should also be included in the suspects list.
2. The constable said "A knife with bloodstain placed inside a novel between pages thirty-five and thirty-six, the finger print on the knife matches with that of suspect B.".  It is practically impossible for a person to place anything between pages 35 and 36. Take a book and try it for yourself.

Thou there are 75% probability of cook being the murderer, 50% probability of other 3 suspects being the murderer, all these become invalid if constable has made up stories in giving primary data.

The the only person who is lying here is constable. It is not usual for a trained constable to make up stories, so by which I concluded constable to be the murderer with 100% probability.

Constable: Yes, I murdered her. I killed her because her father killed my innocent father when I was young. Her father was a rowdy in our area. This was the right time for me to take revenge on their family. I thought you will never find me. Detective Jack, you did it.
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