Murder mystery logic puzzles

A murder mystery logic puzzle is a logic grid with a body in it. Clues tell you who was where; once everyone is placed, the answer to whodunit is sitting on the board.

Where the logic grid comes from

Logic grid puzzles go back at least to the “Zebra puzzle,” printed in Life International in 1962: five houses, five owners, a list of clues, and a single answer that follows from them. Puzzle magazines made the format a staple. More recently, Murdle by G. T. Karber, a daily puzzle that grew into a series of books, put a murder at the centre of the grid, and daily browser deduction games like Clues by Sam brought the same pleasure to a quick daily habit.

How to solve one

• Place the certain ones first. A clue like “Ada was in the Spiral Stairs” fixes a room. Pair it with a row or column clue and the person is fixed to one square.
• Cross off with every “not.” “Cora was not in the Oil Shed” rules out squares. Mark them; negative clues do most of the work.
• Use the one-per-line rule. If each row and column holds one person, a placed person rules out their whole row and column for everyone else.
• Look for the last square. When a person has only one square left, they go there, and that often unlocks the next.
• Never guess. A well-made puzzle has exactly one answer. If you are guessing, a clue has more to give.

Daily Sleuth: a free murder grid every day

Daily Sleuth is our daily take. Each case is a floor plan cut into rooms, five people and a handful of clues. Place everyone so each row and column holds one person and every clue is true. The murderer is the one person left alone in a room with the victim. A new case comes out every day, free, and every grid has exactly one solution.

Stuck? The daily hint page gives three steps, each behind a tap: a nudge, a bigger hint, then one placement. It never names the murderer.

If you like logic grids, try evidence

The same habit of ruling things out works on messier evidence. In Her Backup Phone the clues are text messages and access logs instead of tidy sentences, and you have to prove your answer with two records.